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State assault weapons bans are associated with fewer fatalities: analysis of US county mass shooting incidents (2014-2022)

Background

The need for evidence to inform interventions to prevent mass shootings (MS) in the USA has never been greater.

Methods

Data were abstracted from the Gun Violence Archive, an independent online database of US gun violence incidents. Descriptive analyses consisted of individual-level epidemiology of victims, suspected shooters and weapons involved, trends and county-level choropleths of population-level incident and fatality rates. Counties with and without state-level assault weapons bans (AWB) were compared, and we conducted a multivariable negative binomial model controlling for county-level social fragmentation, median age and number of gun-related homicides for the association of state-level AWB with aggregate county MS fatalities.

Results

73.3% (95% CI 72.1 to 74.5) of victims and 97.2% (95% CI 96.3 to 98.3) of shooters were males. When compared with incidents involving weapons labelled ‘handguns’, those involving a weapon labelled AR-15 or AK-47 were six times more likely to be associated with case-fatality rates greater than the median (OR=6.1, 95% CI 2.3 to 15.8, p<0.00001). MS incidents were significantly more likely to occur on weekends and during summer months. US counties in states without AWB had consistently higher MS rates throughout the study period (p<0.0001), and the slope for increase over time was significantly lower in counties with AWB (beta=–0.11, p=0.01). In a multivariable negative binomial model, counties in states with AWB were associated with a 41% lower incidence of MS fatalities (OR=0.58, 95% CI 0.37 to 0.97, p=0.02).

Conclusions

Counties located in states with AWB were associated with fewer MS fatalities between 2014 and 2022.

Renewing Assault Weapons Ban Could Have Prevented Mass Shootings

Between 1994 and 2004, the federal assault weapons ban prohibited the sale and manufacture of certain military-style semiautomatic weapons and high-capacity magazines in the US. A study in JMIR Public Health and Surveillance now suggests that the ban not only prevented an estimated 5 public mass shootings during those 10 years, but would have averted many more between 2005 and 2022 if it had stayed in place instead of being allowed to expire.

Can Mass Shootings be Stopped?

The mass shooting at Columbine High School in Littleton, Colorado, happened nearly two decades ago, yet it remains etched in the national consciousness. Columbine spurred a national debate — from personal safety to the security of schools, workplaces, and other locations and to broader considerations of guns and mental illness. To this day, communities still are grappling to find solutions to the complex and multifaceted nature of mass shootings.

Deconstructing Mass Shootings: Exploring Opportunities for Intervention

When it comes to mass shootings, the United States is tragically in a class of its own. There are more mass public shootings in the US than in any other country in the world (Lankford, 2016). By some estimates the United States has experienced 318 mass public shootings between 1966 and 2017 (Capellan, Johnson, Porter, & Martin, 2019). These attacks resulted in 1,167 dead and 1,777 injured victims. Unfortunately, mass public shootings show no signs of slowing down. Most research indicates that the rate of mass public shootings has been accelerating over time. For example, Joel Capellan finds that in the 1970s a mass shooting occurred, on average, every 608 days. By the current decade, a mass public shooting occurred, on average, every 20 days. Due to their reoccurring and devastating nature, mass public shootings are starting to be considered a major public health hazard.

Research on mass public shootings has focused almost exclusively on either the characteristics of offenders or the causes leading to these massacres. Although this research is invaluable to our theoretical understanding of the sociological and psychological factors that lead to mass public shootings, it has yet to provide an actionable understanding of how to prevent or mitigate the lethality of these massacres. In this policy report, we argue that prevention requires us to refocus our attention from why to how mass public shootings happen. To this end, we deconstruct mass public shootings into a series of stages and decisions and explore various opportunities for intervention. We analyze the motivations, preparatory behaviors, execution, and conclusion of 318 mass public shootings in the United States between 1966 and 2017. Furthermore, we offer some potential policy solutions to exploit these opportunities for intervention.

Can Mass Shootings be Stopped?

The first five months of 2021 saw high-profile public mass shootings in cities across the United States of America, like Atlanta, Georgia (March 16, 8 dead), Boulder, Colorado (March 22, 10 dead), Indianapolis, Indiana (April 15, 8 dead), and San Jose, California (May 26, 9 dead). Following a year where such events rarely made headlines as the nation found itself in the throes of the coronavirus pandemic, these incidents revived the public discourse about mass shootings in America, as well as how to prevent and respond to such tragedies. This dialogue raised an important question: As society returns to normal after the COVID-19 pandemic, what does the future of mass shootings look like?

To answer this, it is important to understand the trends associated with the phenomenon of mass shootings. The first issuance of this policy brief in 2018 examined 51 years (1966-2016) of mass shootings data based on a comprehensive database from researchers Jaclyn Schildkraut and H. Jaymi Elsass. As described below, the researchers developed their own definition that became the foundation of this analysis given deficiencies with existing classifications and data sources.

This updated brief provides analyses including an additional four new years of data since the original 2018 policy brief to identify changes in trends and broader considerations for policymakers, particularly given the COVID-19 pandemic’s impact and lessons learned from specific shootings within this period. Specifically, this brief presents and analyzes a total of 55 years of mass shooting data from 1966 to 2020, including frequency, injury and fatality, location type, weapon usage, and perpetrator demographics. The appendix contains information on only the most recent four years of data from 2017 to 2020.

Although all episodes of firearm violence are cause for concern, public mass shootings differ from other incidents in key ways. For instance, unlike family murders and a considerable portion of gang violence that may be targeted, public mass shootings are random in nature. They also typically involve considerable planning, rather than other incidents that are more spontaneous in nature, which can provide important opportunities to deescalate the situation before it culminates in the mass shooting. Similarly, the location selection—large, often open public spaces—presents significant challenges for both preventative security measures and responses from law enforcement to active shooter incidents. As such, better understanding this phenomenon in its unique context is necessary to distinguish strategies needed to prevent and respond to public mass shootings. Promoting a deeper understanding of mass shootings can also provide policymakers with important insights upon which to craft more effective prevention and response efforts.