Contagion in Mass Killings and School Shootings

Expanding High School Counseling in a Social Media World: Improving Student and Community Well-Being

Adolescent competence and resilience are indicators of adulthood behavior. High school is a pivotal time for adolescents to foster a stable temperament for adult development. The contemporary state of adolescent depression prevalence and an increase in social media-related risky behavior calls for an update to mental health services. We review the nature of modern social comparison that is fueled by social media, mental health help-seeking stigma that prevents individuals from seeking services, and provide mental health advances to remedy the severity of mental health concerns in a social media society. Social media distortions of normative life promote a standard of expectations that can decrease self-esteem and increase depressive tendencies. Expanding high school counseling such that students see a counselor multiple times a year in a proactive rather than reactive school counseling system can provide transformative changes to community mental health.

Associations between feelings of safety, concerns about firearms on campus and suicidal thoughts and behaviours among college students

BACKGROUND

Perceptions of safety on campus may be related to a variety of factors such as concerns about campus violence, especially firearm violence, and mental health, particularly suicidal thoughts and behaviours (STBs). The present analyses aim to describe associations between feelings of safety, concerns about firearms on campus and STBs among college students.

METHODS

This study uses data from the American College Health Association-National College Health Assessment wave III (n=24 682 participants across k=29 schools). Multilevel logistic regressions and cumulative link mixed models examine the associations between feelings of safety, concerns about firearm violence on campus and presence of STBs in the past year.

RESULTS

Participants who reported being concerned about firearm violence felt significantly less safe. Feeling unsafe at night was significantly associated with suicidal ideation and suicide attempts. Individuals with concerns about firearm safety on campus were up to 42% more likely to report suicidal ideation compared with those reporting they were not at all concerned about campus firearm violence.

DISCUSSION

With associations highlighting increased risk of STBs among those with reduced safety feelings and heightened concerns about firearms, there is a need for college campuses to intervene and promote campus safety, with particular consideration for the presence of firearms on campus and the implications of allowing such weapons to be present in environments with increasing instances of firearm violence.

Examining media reports of pediatric unintentional firearm injury deaths for prevention messaging concerning secured storage of firearms: U.S., 2021-2022

BACKGROUND

Media outlets that report on firearm injuries and deaths may provide an important role in emphasizing safe storage practices, particularly when unintentional firearm injuries and deaths occur among young children. There has been a scarcity of research on aspects of media reports on injuries, particularly concerning prevention messaging. The objective of the present study was to examine prevention messaging on the safe storage of firearms among media outlets when reporting on unintentional firearm injury deaths among children aged 0-11.

METHODS

The Gun Violence Archive collects information from media sources regarding firearm injuries and deaths. We analyzed data from 2021 to 2022 to analyze prevention messaging incorporated into the media reports. We then examined if media reporting of events that occurred in States with child access prevention (CAP) laws had a higher likelihood of including prevention messaging compared to those events occurring in States without CAP laws.

RESULTS

There were 223 deaths reported that were attributed to unintentional firearm discharge among children aged 0-11. Prevention messages were delivered in 61 of the 223 incidents. Specific messages which included the word "lock" when referring to firearm storage were included in 21.9% of all incidents. An analysis examining State CAP laws and the presence of any prevention message per event did not yield any discernable relationship.

CONCLUSION

Inclusion of prevention messaging stating that firearms should be stored locked and unloaded when reporting on unintentional firearm injury deaths among children is lacking. When specific prevention messaging was included, the source was often law enforcement. Public health officials may play an important role in educating the journalistic and law enforcement communities about the inclusion of safe storage messages when reporting on firearm deaths.

Point-process modeling of secondary crashes

Secondary crashes or crashes that occur in the wake of a preceding or primary crash are among the most critical incidents occurring on highways, due to the exceptional danger they present to the first responders and victims of the primary crash. In this work, we developed a self-exciting temporal point process to analyze crash events data and classify it into primary and secondary crashes. Our model uses a self-exciting function to describe secondary crashes while primary crashes are modeled using a background rate function. We fit the model to crash incidents data from the Florida Department of Transportation, on Interstate-4 (I-4) highway for the years 2015-2017, to determine the model parameters. These are used to estimate the probability that a given crash is secondary crash and to find queue times. To represent the periodically varying traffic levels and crash incidents, we model the background rate, as a stationary function, a sinusoidal non-stationary function, and a piecewise non-stationary function. We show that the sinusoidal non-stationary background rate fits the traffic data better and replicates the daily and weekly peaks in crash events due to traffic rush hours. Secondary crashes are found to account for up to 15.09% of traffic incidents, depending on the city on the I-4 Highway.

Database discrepancies in understanding the burden of mass shootings in the United States, 2013-2020

Background

The United States experiences more mass shootings than any other nation in the world. Various entities have sought to collect data on this phenomenon, but there is no scholarly consensus regarding how best to define mass shootings. As a result, existing datasets include different incidents, limiting our understanding of the impact of mass gun violence in the U.S.

Methods

We compared five datasets of mass shootings for each year included in five databases (2013-2020) and identified overlaps between each database's incidents. These overlaps and divergences between datasets persisted after applying the strictest fatality threshold (four or more) in mass shootings scholarship and policy.

Findings

The datasets collectively include 3155 incidents, but the number of incidents included in each individual dataset varies from 57 to 2955 incidents. Only 25 incidents (0.008% of all incidents) are included in all five datasets. This finding persists even when applying the strictest criteria for mass shootings (four or more fatalities).

Interpretation

Data discrepancies prevent us from understanding the public health impact of mass gun violence. These discrepancies result from a lack of scholarly consensus on how to define mass shootings, likely the downstream consequence of the politicization of gun violence research. We argue for a broad definition of a mass shooting and a government-supported data collection program to remedy these discrepancies. Such steps can improve the quality of research and support policy-making and journalism on the subject.

Funding

This research was supported by the Pahl Initiative on the Study of Critical Social Issues, University of California, Santa Barbara.

An Examination of US School Mass Shootings, 2017-2022: Findings and Implications

OBJECTIVES

Gun violence in the USA is a pressing social and public health issue. As rates of gun violence continue to rise, deaths resulting from such violence rise as well. School shootings, in particular, are at their highest recorded levels. In this study, we examined rates of intentional firearm deaths, mass shootings, and school mass shootings in the USA using data from the past 5 years, 2017-2022, to assess trends and reappraise prior examination of this issue.

METHODS

Extant data regarding shooting deaths from 2017 through 2020 were obtained from the Centers for Disease Control and Prevention, National Center for Injury Prevention and Control, the web-based injury statistics query and reporting system (WISQARS), and, for school shootings in particular (2017-2022), from Everytown Research & Policy.

RESULTS

The number of intentional firearm deaths and the crude death rates increased from 2017 to 2020 in all age categories; crude death rates rose from 4.47 in 2017 to 5.88 in 2020. School shootings made a sharp decline in 2020-understandably so, given the onset of the COVID-19 pandemic and subsequent government or locally mandated school shutdowns-but rose again sharply in 2021.

CONCLUSIONS

Recent data suggest continued upward trends in school shootings, school mass shootings, and related deaths over the past 5 years. Notably, gun violence disproportionately affects boys, especially Black boys, with much higher gun deaths per capita for this group than for any other group of youth. Implications for policy and practice are provided.

Guns on campus: An autoethnography of “concealed carry” policies

In the United States, school shootings are a common social problem and frequently occur on both K-12 and college campuses. High profile school shootings have resulted in a growing number of state governments legalizing “concealed carry” on college campuses, increasing the presence of guns in classrooms. This research study employs qualitative autoethnography to present the author's experiences teaching on a campus where concealed carry was implemented in 2014. Through autoethnographic narratives, the author describes her lived experiences. This paper analyses these narratives using intersectional feminist theory and situates the narratives within the broader socio-cultural context of gun culture in the Pacific Northwestern USA. The author spent four years immersed in the culture of concealed carry, and has written multiple narratives detailing these experiences. Two narratives are presented in this work. Important findings in this work include examinations of: how the presence of guns in college classrooms shapes power dynamics; the use of fear-based curricula in active-shooter survival trainings; the cultural construction of the “good guy with a gun”; and the implications of the author's positionalities within gun culture. This research study encourages the reader to engage with and learn from the lived experiences of the author.

Contingencies of Violent Radicalization: The Terror Contagion Simulation

This paper builds confidence in the terror contagion hypothesis that violent radicalization leading to predatory mass violence operates as a system. Within this system, the contingent values of key root causes create channels within which violent ideologies and terrorism emerge. We built a system dynamics simulation model capable of replicating historical reference modes and sophisticated enough to test the contingent values of these propositions. Of 16 propositions, we identified six root-cause propositions that must simultaneously exist, act in concert and explain the dynamics of their interaction which generate a terror contagion. Other propositions can strengthen or weaken an existing contagion but not eliminate it. We use an experiment to demonstrate how changing the contingent values of these propositions creates downward channels. This experiment helps reconcile the swarm vs. fishermen debate over the true root causes of violent radicalization. Within these channels, the contingent values can favor swarm or fishermen manifestations. The simulation and experimentation results enable the future development of the terror contagion hypothesis, provide a testing environment for research on violent radicalization, and provide a pathway to policy development in the combating of terrorism that arises from violent radicalization.

Modeling the Process of School Shooters Radicalization (Russian Case)

Research on radicalization became relevant to the study of terrorism and violent extremism just two decades ago. The accumulated empirical data on terrorism have led researchers and experts to understand that radicalization is a predictor of violent actions by terrorists, violent extremists, and lone actors. Violent incidents committed by school shooters are not terrorist crimes, but there is good reasons for inclusion as terrorist crimes since they have similar mechanisms. The article aims to create a conceptual model of school-shooter radicalization and determine the distinguishing features of the process. The paper presents a theoretical and methodological base of content analysis concepts, political models, and terrorist radicalization on the different levels of study. Based on the content analysis results, we identify the significant gaps in the research field, consider the radicalization phenomenon in detail, substantiated the qualitative aspects of the school shooters radicalization, and propose a conceptual scheme. Psychological, behavioral, cognitive aspects of the school shooters radicalization reflect a holistic picture of the relationship between the process phases and changes in the parameters of the object’s state. The aspects of radicalization and this phenomenon’s qualitative properties are interpreted as the determinants of the conceptual model. The model includes five stages, each of which is considered to be one of the components for the formation and acceptance of the idea of a violent way to solve a problem, but certainly do not act individually as the only component that leads to the actual implementation of the incident of a school shooting. An in-depth study of online social connections and warning signs, mobilization factors, behavioral trajectories, and imitation mechanisms can help scientists understand why school shooters are increasingly motivated to use violent means to achieve personal goals. We have outlined the possibilities and prospects of the model’s application and directions for future research.

Charity Misconduct on Public Health Issues Impairs Willingness to Offer Help

Charity organizations positively impact our societies but charity misconduct impairs people’s willingness to contribute to charity and functional health systems on public health issues. This study investigates the impact of charity misconduct on people’s willingness to offer help on public health issues and possible ways of reducing the negative impact brought by charity misconduct news through four studies (N_total = 1269). Results showed that charity misconduct on public health issues significantly reduced individuals’ willingness to offer help via both the charity involved with the misconduct and any charity they prefer (Study 1 and 2). Furthermore, news on charity misconduct reduced people’s general willingness to help in contexts that did not involve charity (Study 3). Finally, presenting charity nonmisconduct news after charity misconduct news increases individuals’ willingness to offer help via the nonmisconduct charity (Study 4), suggesting a potential way to nudge people to provide help in the fight against the negative impact brought by charity misconduct news. The findings show the backfire of reporting charity misconduct news and have important implications for potential ways to facilitate people to offer help.

Communication of Intent to Do Harm Preceding Mass Public Shootings in the United States, 1966 to 2019

IMPORTANCE

Understanding the motivation of a mass shooter's intent to do harm can help practitioners and policy makers develop more effective intervention strategies.

OBJECTIVE

To examine the prevalence of communication of intent to do harm, known as leakage, in a sample of 170 mass public shooters from 1966 to 2019; the characteristics of perpetrators who do and do not leak their plans; and whether leakage is a form of fame-seeking behavior or a cry for help among individuals who are in crisis or suicidal.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included perpetrators who killed 4 or more people in a public space from 1996 to 2019 and were included in a comprehensive database of US mass shootings. That database was built from August 2017 to December 2019, and analysis took place from January to May 2021.

MAIN OUTCOMES AND MEASURES

Leakage was identified and coded using publicly available records. Any communication to a third party of an intent to do harm prior to the shooting was coded as leakage. Logistic regression models were used to examine the risk factors associated with leakage. Models estimating leakage were examined to assess the 2 hypothesized pathways to leakage (the cry-for-help model and the fame-seeking model).

RESULTS

The 170 participants in this sample included 166 (97.7%) male perpetrators and 3 (2.3%) female perpetrators, with a mean (SD) age of 34 (12) years. Overall, 161 participants had known race and ethnicity: 11 (6.8%) Asian individuals, 35 (21.7%) Black individuals, 14 (8.7%) Latinx individuals, 7 (4.4%) Middle Eastern individuals, 3 (1.9%) Native American individuals, 89 (55.3%) White individuals, and 2 (1.2%) individuals with other race and ethnicity. Overall, 79 mass shooters (46.5%) leaked their plans. Of perpetrators who leaked their plans, 35 (44.3%) leaked specific plans about a mass shooting, and 44 (55.1%) leaked nonspecific plans about generalized violence. The study findings indicate that leakage was associated with receiving counseling (odds ratio, 7.0; 95% CI, 2.0-24.8) and suicidality (odds ratio, 3.7; 95% CI, 1.0-13.6), suggesting that leakage may best be characterized as a cry for help from perpetrators prior to their act.

CONCLUSIONS AND RELEVANCE

In this study, nearly half of the perpetrators of mass shootings leaked their plans. Leakage was associated with receiving counseling and suicidality. Leakage is a critical moment for mental health intervention to prevent gun violence. Opportunities to report threats of violence need to be increased. Traditional threat assessment models focused on specific threats of violence may miss critical opportunities for intervention.

A Within-Individual Examination of the Predictors of Gun Carrying During Adolescence and Young Adulthood Among Young Men

Although prior studies have identified several risk factors for gun carrying, no prior longitudinal studies have examined a comprehensive set of explanatory factors together in within-individual change models or examined whether the predictors of gun carrying change across adolescence and early young adulthood. The present study fills these gaps by examining the predictive utility of several risk factors for gun carrying, and by examining whether any of the associations vary by age. The sample included 1216 young men who were arrested for the first time during adolescence (approximately 15 years old) and interviewed regularly for 5 years (until approximately 20 years old) after the first arrest. The outcome was youth-self-reported gun carrying and the risk factors included several variables consistent with various explanations for gun carrying (psychosocial maturity deficits; antisocial behavioral style; socialization; victimization). Research questions were addressed with fixed effects dynamic panel models (within-individual change models). Results showed that the most robust predictors of gun carrying were increased exposure to guns and gun-related violence and increased engagement in other antisocial and illegal behavior. The results emphasize the specific etiology of gun carrying and the potential social contagion effect of gun-related events. Overall, the study points to the need for prevention and intervention programs to specifically target the reduction of the real and perceived prevalence of gun-related events in young men's lives.

Examining differences between mass, multiple, and single-victim homicides to inform prevention: findings from the National Violent Death Reporting System

Background

Multi-victim homicides are a persistent public health problem confronting the United States. Previous research shows that homicide rates in the U.S. are approximately seven times higher than those of other high-income countries, driven by firearm homicide rates that are 25 times higher; 31% of public mass shootings in the world also occur in the U.S.. The purpose of this analysis is to examine the characteristics of mass, multiple, and single homicides to help identify prevention points that may lead to a reduction in different types of homicides.

Methods

We used all available years (2003–2017) and U.S. states/jurisdictions (35 states, the District of Columbia, and Puerto Rico) included in CDC’s National Violent Death Reporting System (NVDRS), a public health surveillance system which combines death certificate, coroner/medical examiner, and law enforcement reports into victim- and incident-level data on violent deaths. NVDRS includes up to 600 standard variables per incident; further information on types of mental illness among suspected perpetrators and incident resolution was qualitatively coded from case narratives. Data regarding number of persons nonfatally shot within incidents were cross-validated when possible with several other resources, including government reports and the Gun Violence Archive. Mass homicides (4+ victims), multiple homicides (2-3 victims) and single homicides were analyzed to assess group differences using Chi-square tests with Bonferroni-corrected post-hoc comparisons.

Results

Mass homicides more often had female, child, and non-Hispanic white victims than other homicide types. Compared with victims of other homicide types, victims of mass homicides were more often killed by strangers or someone else they did not know well, or by family members. More than a third were related to intimate partner violence. Approximately one-third of mass homicide perpetrators had suicidal thoughts/behaviors noted in the time leading up to the incident. Multi-victim homicides were more often perpetrated with semi-automatic firearms than single homicides. When accounting for nonfatally shot victims, over 4 times as many incidents could have resulted in mass homicide.

Conclusions

These findings underscore the important interconnections among multiple forms of violence. Primary prevention strategies addressing shared risk and protective factors are key to reducing these incidents.

Assessing the contagiousness of mass shootings with nonparametric Hawkes processes

Gun violence and mass shootings are high-profile epidemiological issues facing the United States with questions regarding their contagiousness gaining prevalence in news media. Through the use of nonparametric Hawkes processes, we examine the evidence for the existence of contagiousness within a catalog of mass shootings and highlight the broader benefits of using such nonparametric point process models in modeling the occurrence of such events.

Feeling Unsafe at School and Associated Mental Health Difficulties among Children and Adolescents: A Systematic Review

This study systematically reviewed the literature on perceived school safety. We investigated the prevalence, factors and associated mental health difficulties, as well as cross-cultural findings. Five databases were searched up to 9 February 2021 for peer-reviewed papers published in English. We included quantitative studies that explored the perception of school safety among children and adolescents. The reference lists of the selected papers were also searched. We conducted a narrative synthesis of the included studies. The review included 43 papers. The mean prevalence of the students who felt unsafe at school was 19.4% and ranged from 6.1% to 69.1%. Their perceived safety was associated with a wide range of personal, school, and social factors. Not feeling safe at school was related to being victimized and mental health difficulties, including depressive symptoms and suicidal behavior. Higher perceived school safety was associated with measures such as the presence of a security officer and fair school rule enforcement. The results showed the lack of cross-cultural studies on perceived school safety. Empirical studies are needed that examine the mechanisms of school safety, using valid measures. A clear definition of school safety should be considered a key aspect of future studies.

A Multivariate Comparison of Family, Felony, and Public Mass Murders in the United States

The mass murderer is known by a variety of names in both public and academic spheres, from the family annihilator to the active shooter, from the workplace avenger to the rampage school shooter. Although most researchers acknowledge that the phenomenon is heterogeneous, mass killing has defied classification, and currently no consensus typology exists. Most previous efforts at developing a classification scheme have focused on sorting these multicides into three broad groups, namely, family, felony, and public mass killings, exclusively relying on qualitative methods and case-study analysis to do so. The present study employs a multivariate approach to examine differences among types in victim, offender, and incident characteristics on the population of all mass murders in the United States from 2006 to 2016.

Australian Mass Shootings: An Analysis of Incidents and Offenders

Mass shooting events are relatively underresearched, and most study comes from the United States. Despite significant international interest, little is known about other countries' experiences of these events. The current study examines Australian mass shooting incidents and offenders, with emphasis on mental illness, life strains, and offenders' life histories. Australia had 14 mass shootings between 1964 and 2014. Most offenders experienced acute life stressors and/or chronic strains leading up to the event; however, diagnosed mental illness was less commonly documented. These observations provide new information about mass shooting incidents and offenders, and can help to inform international policy development.

Self-Protection versus Fear of Stricter Firearm Regulations: Examining the Drivers of Firearm Acquisitions in the Aftermath of a Mass Shooting

Discovering causal mechanisms underlying firearm acquisition can provide critical insight into firearm-related violence in the United States. Here, we established an information-theoretic framework to address the long-disputed dichotomy between self-protection and fear of firearm regulations as potential drivers of firearm acquisition in the aftermath of a mass shooting. We collected data on mass shootings, federal background checks, media output on firearm control and shootings, and firearm safety laws from 1999 to 2017. First, we conducted a cluster analysis to partition States according to the restrictiveness of their firearm-related legal environment. Then, we performed a transfer entropy analysis to unveil causal relationships at the State-level in the Wiener-Granger sense. The analysis suggests that fear of stricter firearm regulations is a stronger driver than the desire of self-protection for firearm acquisitions. This fear is likely to cross State borders, thereby shaping a collective pattern of firearm acquisition throughout the Nation.

The Christchurch mosque shooting, the media, and subsequent gun control reform in New Zealand: a descriptive analysis

In March 2019, a mass shooting at two Christchurch mosques, livestreamed to Facebook, resulted in the deaths of 51 people. Psychologically, this served as a focusing event with high threat salience, shocking a country unused to gun violence despite its comparatively lax firearm legislation. The unprecedented reluctance by the New Zealand media to feature the shooter as a protagonist or even publish his name, concentrating instead on victims and societal issues, helped promote a sense of collective responsibility for change. This was strongly modeled by political leaders. Within weeks, new gun control laws were introduced with bipartisan support. We present this as a national case study, considering psychological and societal enablers for legislative reform in response to extreme gun violence. The shooting also raised the intractable problem of the internet allowing terrorists to promulgate violent content and extremist ideology with regulation in this area harder to achieve than gun control.

Killer Folklore

This article considers the development of identity within the True Crime Community (TCC) and examines the contagion theory of crime surrounding serial and mass murder within the United States. The TCC is an online Tumblr group that shares pictures, jokes, legends and other narratives surrounding such killers. TCC members are frequently blamed by outsiders for creating spaces where killers become celebrities which, in theory, creates more killers. Two issues arise out of contagion theory. The first is that modes of participation with crime representations and the production of texts around true crimes is shaped by contagion theory and vernacular debates about fandom. Second, contagion theory itself is open to critical cross disciplinary investigation for which folklorists, examining communities who participate in (re)producing true crime texts can offer valuable data, approaches and theory. Moreover, as folklorists working in rumour and contemporary legend have noted, we may have a role to play in interrupting crime cycles themselves.

Fuel shortages during hurricanes: Epidemiological modeling and optimal control

Hurricanes are powerful agents of destruction with significant socioeconomic impacts. A persistent problem due to the large-scale evacuations during hurricanes in the southeastern United States is the fuel shortages during the evacuation. Computational models can aid in emergency preparedness and help mitigate the impacts of hurricanes. In this paper, we model the hurricane fuel shortages using the SIR epidemic model. We utilize the crowd-sourced data corresponding to Hurricane Irma and Florence to parametrize the model. An estimation technique based on Unscented Kalman filter (UKF) is employed to evaluate the SIR dynamic parameters. Finally, an optimal control approach for refueling based on a vaccination analogue is presented to effectively reduce the fuel shortages under a resource constraint. We find the basic reproduction number corresponding to fuel shortages in Miami during Hurricane Irma to be 3.98. Using the control model we estimated the level of intervention needed to mitigate the fuel-shortage epidemic. For example, our results indicate that for Naples- Fort Myers affected by Hurricane Irma, a per capita refueling rate of 0.1 for 2.2 days would have reduced the peak fuel shortage from 55% to 48% and a refueling rate of 0.75 for half a day before landfall would have reduced to 37%.

Effect of mass shootings on gun sales-A 20-year perspective

BACKGROUND

Granular data on gun sales has been historically difficult to obtain. In 2016, California (CA) made monthly data from 1996 to 2015 publically available. Control charts are a method to analyze how a process changes over time in response to nonroutine events. We utilized this technique to study the impact of US mass shootings on CA gun sales.

METHODS

Monthly gun sales were provided by the CA Department of Justice and monthly fatalities from the CDC Wonder Death Certificate Registry. Mass shooting events were obtained from after-action reports, news media, and court proceedings. Time-ordered data were analyzed with control charts with 95% confidence intervals (upper control limit, lower control limit) using QiMacros.

RESULTS

Individual gun sales of 9,917,811 occurred in CA with a median monthly rate of 41,324 (range, 20,057-132,903). A median of 263 people lost their lives monthly from firearms (124 homicides, 128 suicides), totaling 53,975 fatalities from 1999 to 2015. Fifteen of 21 current deadliest mass shootings occurred during this study period with 40% from 2012 to 2015. Also, 36 school shootings occurred during the study (mean, 5 deaths; range, 0-33; 6 injuries; range, 0-23) with 31% in 2012 to 2015 at rate of 3 events/year versus 1.4 events/year in the 17 prior years (p < 0.05). Sales were generally consistent from 1996 to 2011 (except post-Columbine, Col). Starting in 2011, sales exceeded the 95% predicted upper control limit every single month. Before October 2011, there was no statistically significant sustained effect of mass shootings on sales (except Col); however, since a statistically significant proportional spike in sales occurred in the months immediately following every single deadliest mass shooting event. Every year since 2012, CA has strengthened gun laws in response to mass shootings yet sales have risen immediately preceding enactment of these laws each January.

CONCLUSION

Gun sales are more frequent since 2012, with an additional increase following both mass shootings and legislative changes enacted in response to these shootings.

LEVEL OF EVIDENCE

Epidemiology, level III.

A Tour of the Basic Reproductive Number and the Next Generation of Researchers

The Mathematical and Theoretical Biology Institute (MTBI) is a national award winning Research Experience for Undergraduates (REU) that has been running every summer since 1996. Since 1997, students have developed and proposed their own research questions and derived their research projects from them as the keystone of the program. Because MTBI’s mentors have no control over what students are interested in, we need to introduce a suite of flexible techniques that can be applied to a broad variety of interests. In this paper, we walk through examples of some of the most popular techniques at MTBI: epidemiological or contagion modeling and reproductive number analysis. We include an overview of the next generation matrix method of finding the basic reproductive number, sensitivity analysis as a technique for investigating the effect of parameters on the reproductive number, and recommendations for interpreting the results. Lastly, we provide some advice to mentors who are looking to advise student-led research projects. All examples are taken from actual student projects that are generally available through the MTBI website.

Mass School Shootings in the United States: A Novel Root Cause Analysis Using Lay Press Reports

School shootings comprise a small proportion of childhood deaths from firearms; however, these shootings receive a disproportionately large share of media attention. We conducted a root cause analysis of 2 recent school shootings in the United States using lay press reports. We reviewed 1760 and analyzed 282 articles from the 10 most trusted news sources. We identified 356 factors associated with the school shootings. Policy-level factors, including a paucity of adequate legislation controlling firearm purchase and ownership, were the most common contributing factors to school shootings. Mental illness was a commonly cited person-level factor, and access to firearms in the home and availability of large-capacity firearms were commonly cited environmental factors. Novel approaches, including root cause analyses using lay media, can identify factors contributing to mass shootings. The policy, person, and environmental factors associated with these school shootings should be addressed as part of a multipronged effort to prevent future mass shootings.

Media coverage and firearm acquisition in the aftermath of a mass shooting

With an alarming frequency, the United States is experiencing mass shooting events, which often result in heated public debates on firearm control. Whether such events play any role in recent dramatic increases in firearm prevalence remains an open question. This study adopts an information-theoretic framework to analyse the complex interplay between the occurrence of a mass shooting, media coverage on firearm control policies and firearm acquisition at both national and state levels. Through the analysis of time series from 1999 to 2017, we identify a correlation between the occurrence of a mass shooting and the rate of growth in firearm acquisition. More importantly, a transfer entropy analysis pinpoints media coverage on firearm control policies as a potential causal link in a Wiener-Granger sense that establishes this correlation. Our results demonstrate that media coverage may increase public worry about more stringent firearm control and partially drive increases in firearm prevalence.

Evolution and study of a copycat effect in intimate partner homicides: A lesson from Spanish femicides

Objectives

This paper focuses on the issue of intimate partner violence and, specifically, on the distribution of femicides over time and the existence of copycat effects. This is the subject of an ongoing debate often triggered by the social alarm following multiple intimate partner homicides (IPHs) occurring in a short span of time. The aim of this research is to study the evolution of IPHs and provide a far-reaching answer by rigorously analyzing and searching for patterns in data on femicides.

Methods

The study analyzes an official dataset, provided by the system VioGén of the Secretaría de Estado de Seguridad (Spanish State Secretariat for Security), including all the femicides occurred in Spain in 2007-2017. A statistical methodology to identify temporal interdependencies in count time series is proposed and applied to the dataset. The same methodology can be applied to other contexts.

Results

There has been a decreasing trend in the number of femicides per year. No interdependencies among the temporal distribution of femicides are observed. Therefore, according to data, the existence of copycat effect in femicides cannot be claimed.

Conclusions

Around 2011 there was a clear change in the average number of femicides which has not picked up. Results allow for an informed answer to the debate on copycat effect in Spanish femicides. The planning of femicides prevention activities should not be a reaction to a perceived increase in their occurrence. As a copycat effect is not detected in the studied time period, there is no evidence supporting the need to censor media reports on femicides.

Media exposure to mass violence events can fuel a cycle of distress

The established link between trauma-related media exposure and distress may be cyclical: Distress can increase subsequent trauma-related media consumption that promotes increased distress to later events. We tested this hypothesis in a 3-year longitudinal study following the 2013 Boston Marathon bombings and the 2016 Orlando Pulse nightclub massacre using a national U.S. sample (N = 4165). Data were collected shortly after the bombings, 6 and 24 months post-bombings, and beginning 5 days after the Pulse nightclub massacre (approximately 1 year later; 36 months post-bombings). Bombing-related media exposure predicted posttraumatic stress symptoms (PTS) 6 months later; PTS predicted worry about future negative events 2 years after the bombings, which predicted increased media consumption and acute stress following the Pulse nightclub massacre 1 year later. Trauma-related media exposure perpetuates a cycle of high distress and media use.

What have we learned from the time trend of mass shootings in the U.S.?

Little is known regarding the time trend of mass shootings and associated risk factors. In the current study, we intended to explore the time trend and relevant risk factors for mass shootings in the U.S. We attempted to identify factors associated with incidence rates of mass shootings at the population level. We evaluated if state-level gun ownership rate, serious mental illness rate, poverty percentage, and gun law permissiveness could predict the state-level mass shooting rate, using the Bayesian zero-inflated Poisson regression model. We also tested if the nationwide incidence rate of mass shootings increased over the past three decades using the non-homogenous Poisson regression model. We further examined if the frequency of online media coverage and online search interest levels correlated with the interval between two consecutive incidents. The results suggest an increasing trend of mass shooting incidences over time (p < 0.001). However, none of the state-level variables could predict the mass shooting rate. Interestingly, we have found inverse correlations between the interval between consecutive shootings and the frequency of on-line related reports as well as on-line search interests, respectively (p < 0.001). Therefore, our findings suggest that online media might correlate with the increasing incidence rate of mass shootings. Future research is warranted to continue monitoring if the incidence rates of mass shootings change with any population-level factors in order to inform us of possible prevention strategies.

Mass Killings in the United States from 2006 to 2013: Social Contagion or Random Clusters?

In line with previous research on suicide and social contagion, there has been widespread speculation that mass killings-which often involve suicidal offenders-are socially contagious for up to 14 days. This study tested these claims by making comparisons (i) between observed chronological clusters of mass killings in the United States from 2006 to 2013 and clusters in 500 simulations containing 116,000 randomly generated dates, and then (ii) between observed mass killings receiving varying levels of public attention. No evidence of short-term contagion was found, although longer term copycat effects may exist. Further scholarly and policy implications are discussed.

Detecting the contagion effect in mass killings; a constructive example of the statistical advantages of unbinned likelihood methods

Background

When attempting to statistically distinguish between a null and an alternative hypothesis, many researchers in the life and social sciences turn to binned statistical analysis methods, or methods that are simply based on the moments of a distribution (such as the mean, and variance). These methods have the advantage of simplicity of implementation, and simplicity of explanation.

However, when null and alternative hypotheses manifest themselves in subtle differences in patterns in the data, binned analysis methods may be insensitive to these differences, and researchers may erroneously fail to reject the null hypothesis when in fact more sensitive statistical analysis methods might produce a different result when the null hypothesis is actually false.

Here, with a focus on two recent conflicting studies of contagion in mass killings as instructive examples, we discuss how the use of unbinned likelihood methods makes optimal use of the information in the data; a fact that has been long known in statistical theory, but perhaps is not as widely appreciated amongst general researchers in the life and social sciences.

Methods

In 2015, Towers et al published a paper that quantified the long-suspected contagion effect in mass killings. However, in 2017, Lankford & Tomek subsequently published a paper, based upon the same data, that claimed to contradict the results of the earlier study. The former used unbinned likelihood methods, and the latter used binned methods, and comparison of distribution moments.

Using these analyses, we also discuss how visualization of the data can aid in determination of the most appropriate statistical analysis methods to distinguish between a null and alternate hypothesis. We also discuss the importance of assessment of the robustness of analysis results to methodological assumptions made (for example, arbitrary choices of number of bins and bin widths when using binned methods); an issue that is widely overlooked in the literature, but is critical to analysis reproducibility and robustness.

Conclusions

When an analysis cannot distinguish between a null and alternate hypothesis, care must be taken to ensure that the analysis methodology itself maximizes the use of information in the data that can distinguish between the two hypotheses.

The use of binned methods by Lankford & Tomek (2017), that examined how many mass killings fell within a 14 day window from a previous mass killing, substantially reduced the sensitivity of their analysis to contagion effects. The unbinned likelihood methods used by Towers et al (2015) did not suffer from this problem.

While a binned analysis might be favorable for simplicity and clarity of presentation, unbinned likelihood methods are preferable when effects might be somewhat subtle.

The performance of the IES-R for Latinos and non-Latinos: Assessing measurement invariance

Violent acts on university campuses are becoming more frequent. Enrollment rates of Latinos at universities is increasing. Research has indicated that youths are more susceptible to trauma, particularly Latinos. Thus, it is imperative to evaluate the validity of commonly used posttraumatic stress measures among Latino college students. The Impact of Event Scale-Revised (IES-R) is one of the most commonly used metrics of posttraumatic stress disorder symptomatology. However, it is largely unknown if the IES-R is measuring the same construct across different sub-samples (e.g. Latino versus non-Latino). The current study aimed to assess measurement invariance for the IES-R between Latino and non-Latino participants. A total of 545 participants completed the IES-R. One- and three-factor scoring solutions were compared using confirmatory factor analyses. Measurement invariance was then evaluated by estimating several multiple-group confirmatory factor analytic models. Four models with an increasing degree of invariance across groups were compared. A significant χ2 difference test was used to indicate a significant change in model fit between nested models within the measurement invariance testing process. The three-factor scoring solution could not be used for the measurement invariance process because the subscale correlations were too high for estimation (rs 0.92-1.00). Therefore, the one-factor model was used for the invariance testing process. Invariance was met for each level of invariance: configural, metric, scalar, and strict. All measurement invariance testing results indicated that the one-factor solution for the IES-R was equivalent for the Latino and non-Latino participants.

Random Acts of Violence? Examining Probabilistic Independence of the Temporal Distribution of Mass Killing Events in the United States

Recent mass killings, such as those in Newtown, Connecticut, and Aurora, Colorado, have brought new attention to mass killings in the United States. This article examines 323 mass killings taking place between January 1, 2006, and October 4, 2016, to assess how they are distributed over time. In particular, we find that they appear to be uniformly distributed over time, which suggests that their rate has remained stable over the past decade. Moreover, analysis of subsets of these mass killings sharing a common trait (e.g., family killings, public killings) suggests that they exhibit a memoryless property, suggesting that mass killing events within each category are random in the sense that the occurrence of a mass killing event does not signal whether another mass killing event is imminent. However, the same memoryless property is not found when combining all mass killings into a single analysis, consistent with earlier research that found evidence of a contagion effect among mass killing events. Because of the temporal randomness of public mass killings and the wide geographic area over which they can occur, these results imply that these events may be best addressed by systemic infrastructure-based interventions that deter such events, incorporate resiliency into the response system, or impede such events until law enforcement can respond when they do occur.

The Link Between Mental Illness and Firearm Violence: Implications for Social Policy and Clinical Practice

The United States has substantially higher levels of firearm violence than most other developed countries. Firearm violence is a significant and preventable public health crisis. Mental illness is a weak risk factor for violence despite popular misconceptions reflected in the media and policy. That said, mental health professionals play a critical role in assessing their patients for violence risk, counseling about firearm safety, and guiding the creation of rational and evidence-based public policy that can be effective in mitigating violence risk without unnecessarily stigmatizing people with mental illness. This article summarizes existing evidence about the interplay among mental illness, violence, and firearms, with particular attention paid to the role of active symptoms, addiction, victimization, and psychosocial risk factors. The social and legal context of firearm ownership is discussed as a preface to exploring practical, evidence-driven, and behaviorally informed policy recommendations for mitigating firearm violence risk.

Mass Shootings: The Role of the Media in Promoting Generalized Imitation

Mass shootings are a particular problem in the United States, with one mass shooting occurring approximately every 12.5 days. Recently a "contagion" effect has been suggested wherein the occurrence of one mass shooting increases the likelihood of another mass shooting occurring in the near future. Although contagion is a convenient metaphor used to describe the temporal spread of a behavior, it does not explain how the behavior spreads. Generalized imitation is proposed as a better model to explain how one person's behavior can influence another person to engage in similar behavior. Here we provide an overview of generalized imitation and discuss how the way in which the media report a mass shooting can increase the likelihood of another shooting event. Also, we propose media reporting guidelines to minimize imitation and further decrease the likelihood of a mass shooting.

School shootings during 2013-2015 in the USA

BACKGROUND

Data on the factors associated with school shootings in the USA are limited. The public conversation has often suggested several factors that may be linked to these events, however with little empirical support. Aiming to fill this gap, we describe the characteristics of school shooting incidents in the USA between 2013 and 2015 and explore whether four factors that represent domains of firearm policy, educational policy and epidemiological risk factors for intentional firearm injuries-background check (BC) policies, per capita mental health expenditures (MHE), K-12 education expenditure (KEE) and urbanicity-were associated with school shootings during this period.

METHODS

We searched LexisNexis, a newspaper and broadcast media databases for school shooting incidents from 1 January 2013 to 31 December 2015. Presence of BC laws was extracted from legal information in LexisNexis. State-level covariates of per capita MHE (2013), KEE (2013) and urbanicity (2010) rates were obtained from publicly available data sources. We used negative binomial regression models accounting for clustering by state to explore unadjusted associations between the BC laws, state-level covariates and school shootings to report IRR and 95% CI.

RESULTS

We documented 154 school shootings (35, 55 and 64 each year). In unadjusted models, BC for firearm purchase (IRR=0.55, 95% CI 0.39 to 0.76), ammunition purchase (IRR=0.11, 95% CI 0.05 to 0.27), log per capita MHE (IRR=0.58, 95% CI 0.37 to 0.90), log per-capita KEE (IRR=0.09, 9% CI 0.02 to 0.29) and urbanicity (IRR=0.97, 95% CI 0.96 to 0.99) were associated with school shooting.

CONCLUSIONS

School shootings are less likely in states with BC laws, higher MHE and KEE, and with greater per cent urban population.

Understanding Homicide-Suicide

Homicide-suicide is the phenomenon in which an individual kills 1 or more people and commits suicide. Research on homicide-suicide has been hampered by a lack of an accepted classification scheme and reliance on media reports. Mass murder-suicide is gaining increasing attention particularly in the United States. This article reviews the research and literature on homicide-suicide, proposing a standard classification scheme. Preventive methods are discussed and sociocultural factors explored. For a more accurate and complete understanding of homicide-suicide, it is argued that future research should use the full psychological autopsy approach, to include collateral interviews.