By Jillian Peterson, ; Gina Erickson; Kyle Knapp, James Densley

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. 

JAMA Network Open. 2021, 9p.

By Dru Stevenson

Firearm policy in the United States is subject to longstanding political gridlock. Up to now, most of the legal academic literature has focused on the constitutionality of various—or any—regulations regarding firearm possession, sales, or usage. This article inverts the problem and proposes a system for voluntary registration and certification of nonowners, those who want to waive or renounce their Second Amendment rights as a matter of personal conviction. The proposed system is analogous to both the registration of conscientious objectors during wartime conscriptions, and the newer suicide prevention laws whereby individuals can add their names to a do-not-sell list for firearm dealers—though the proposal made here is broader and more permanent. Voluntary registration, with official certification, would serve three important purposes. First, this would help create social identification markers for the gunless-by-choice movement, something that historically has been missing; formal signals and labels of identification with a movement are necessary for a movement’s success, especially with prohibition or abstinence movements. Second, registration and certification as gunless would be a personal moral commitment marker; all societies provide ways for solemnizing one’s vows and solidifying one’s resolve on serious, lifelong moral decisions. Third, certification allows for a market signaling effect, providing useful information that can trigger a beneficial response from the private sector; market responses, in turn, provide useful information about otherwise hotly-debated beliefs, such as whether guns in fact enhance or reduce safety for individuals and public places. This article develops each of these points and offers a unique and simple regulatory and statutory alternative for a new system of registration and certification.

86 Brook. L. Rev. (2021).

by Kelly Drane

In many communities across the country, gun violence has been an unrelenting drumbeat. In a single deadly day, gun violence claimed the lives of a 31-year-old father in Port Allen, Louisiana; a 43-year-old in Philadelphia, Pennsylvania, who was known as a stylish dresser with a great sense of humor; an 11-year-old in Columbia, Missouri, who loved to dance and play with her cousins; and a 17-year-old in Columbus, Ohio, who was a gifted boxer.

Each day, hundreds of lives like these are lost or irrevocably changed as this crisis rages on.

But in the last two years, the tempo of this beat has gotten faster. Gun violence has skyrocketed in cities and towns across the country, leaving more devastation and more trauma in its wake.

More than 45,000 Americans were killed in acts of gun violence in 2020—a 15% increase over the previous year. This increase was primarily driven by an unprecedented 35% rise in gun homicides. In fact, more people were lost to gun violence in 2020 than any other year on record, and although final data is not yet available, the gun death total in 2021 is likely to surpass these records.

This drumbeat is ever-present, but one to which too many have become numb. For too long, this epidemic has gone unchecked, and even as it has spiraled out of control, too many leaders are choosing to do nothing. This moment demands attention, and we must do more to mitigate these increases and protect communities in crisis.

This report provides data describing how gun violence has skyrocketed in 2020 and 2021, showing that this historic rise in gun violence has primarily served to intensify this crisis in communities that already suffered the greatest burden. Additionally, this report describes and considers the factors that most likely contributed to these increases, based on available evidence, and makes suggestions for how policymakers can best respond to this unprecedented challenge.

San Francisco: Giffords Law Center to Prevent Gun Violence., 2022, 3p.

By Leslie M. Barnard; Erin Wright-Kelly; Ashley Brooks-Russell; et al

  Mass shootings (MS) account for less than 1% of firearm deaths in the US, but the frequency has increased.1 Risk factors for MS perpetration include societal discrimination, contagion effects, firearm access, mental illness, and substance abuse.2 Previous geographically and analytically limited studies found MS with handguns had higher fatality rates than those with rifles,3 and following an age-based assault weapons (AWs) restriction there was a reduction in firearm violence from AWs.4 Another study found that the 1994 federal AWs ban was associated with fewer MS.5 To further investigate the association between type of firearm and lethality of MS, this study examined what firearms were present at publicly targeted fatal MS and determined if AWs were associated with a higher number of injuries or deaths.

JAMA Netw Open. 2025;8(2):e2458085. doi:10.1001/jamanetworkopen.2024.58085 4p.

By Silvia Villarreal, Amy Barnhorst, Richard Bonnie, Kami Chavis, Cassandra Crifasi, Shannon Frattaroli, Kelly Roskam, Jeffrey Swanson, Sylvia Washington, and Joshua Horwitz.  

  Firearm purchaser licensing (FPL) laws (sometimes referred to as permit-to-purchase) require an individual to obtain a license through an application process before purchasing a firearm. They are among the most effective policies at reducing gun violence. FPL laws create robust mechanisms of accountability among both prospective gun owners and sellers to ensure that those disqualified from firearm ownership can’t legally obtain a gun. This report compiles existing research to inform state policy. It includes an overview of state FPL laws and recommends core components of FPL laws to maximize public health benefits.

The authors recommend that state gun licensing laws include five core components to maximize public health benefits:

• Firearms safety training

• Fingerprinting

• In-person application

• Comprehensive background checks

• Waiting periods between application and possession of a firearm

Currently 11 states—Connecticut, Delaware, Hawaii, Illinois, Maryland, Massachusetts, Michigan, Nebraska, New Jersey, New York, and Oregon—and Washington, D.C., have active firearm purchasing licensing laws. Of these, five states—Delaware, Hawaii, Massachusetts, New Jersey, Oregon—and Washington, D.C., have the five components recommended in the report.

“There is solid evidence from public health research suggesting that when states adopt firearm purchaser licensing laws with measures such as mandatory safety training, comprehensive background checks, and waiting periods, reductions in gun-related homicides and suicides follow,” says study lead author Silvia Villarreal, MPP, director of research translation at the Johns Hopkins Center for Gun Violence Solutions.

Gun violence is a significant cause of mortality for Americans, and the leading cause of death for children and young people ages 1 to 17. According to the Centers for Disease Control and Prevention, 46,728 people died from gunshots in the U.S. in 2023, the most recent year for which final statistics are available. The 2023 CDC data shows firearms were used in seven out of 10 homicides and 55% of suicides.

U.S. federal law requires background checks for would-be gun buyers at federally licensed gun stores but does not cover private sales or gun shows. Moreover, federal law generally allows a gun sale to proceed if the background check is still pending after three business days. 

The report cites evidence—in many cases generated by the report’s co-authors—that firearm purchaser licensing reduces gun violence. A 2018 study linked gun purchaser licensing laws to an 11% reduction in gun homicides in urban counties across the U.S. from 1984 to 2015. A 2020 study found that gun purchaser licensing laws were associated with 56% fewer mass shooting incidents and 67% fewer mass shooting victims on average. Another 2020 study linked Connecticut’s 1995 handgun purchaser licensing law to a 28% drop in the state’s gun homicide rate and a 33% drop in its gun suicide rate from 1996 to 2017.

Similarly, a 2014 study found that Missouri’s 2007 repeal of its handgun-buyer licensing law was followed by 25% increase in its gun homicide rate in the five years following enactment. A 2015 study found a 16% increase in Missouri’s gun suicide rate in the five years following the repeal.

“This report is an important resource that brings together the research, policy, and legal considerations about firearm purchasing laws,” says Josh Horwitz, JD, co-director of the Center for Gun Violence Solutions. “Our intent is to give policymakers and advocates all the guidance and evidence they need to bring these policies to fruition.” 

The researchers hope that the report will encourage state policymakers to maintain or strengthen existing firearm-purchaser licensing laws and enact firearm purchasing laws in states that don’t yet have them.

Baltimore, MD: The Johns Hopkins Center for Gun Violence Solutions 2025. 30p.

By David Bruce

Mapping gun crimes can ensure that police resources are used in a targeted way to reduce violent offences.

Firearm crime is rife in South Africa. Mapping it can help ensure police resources are used in a targeted way to reduce firearm-related offences. This policy brief illustrates how firearm crime can be mapped by using police data. It focuses on Gauteng province, which has high levels of gun use by criminals.

Key findings Firearms make a major contribution to crime-related death, injury and fear in South Africa. In areas with high firearm crime levels, there are seven main gun-related crime categories: murder, attempted murder, robbery with aggravating circumstances, carjacking, residential robbery, nonresidential robbery and illegal possession of guns and ammunition. South Africa’s highest gun-related crime levels are in the following provinces: Gauteng, Western Cape, KwaZulu-Natal and parts of the Eastern Cape. Recommendations The SAPS should develop a focused strategy to reduce levels of firearm crime and violence. The SAPS should use crime data to identify the areas where firearm crime is most concentrated. This will support the targeted use of resources to reduce firearm crime. Targeted evidence-based strategies are more likely to have a measurable impact on levels of violent crimes associated with firearm use. As an initial step, the SAPS should use available information on ‘instruments’ used in crime from the Crime Administration System (CAS), or docket analysis, to assess levels of firearm crime in each police station area. The results will show the provinces, metropolitan In these provinces, police station areas with the highest levels of crime in the seven main gun-related crime categories are also high firearm-use areas. South African Police Service (SAPS) data on Gauteng police stations with high levels of these seven crimes highlights 41 high firearm crime police stations. Although data collection standards differ between stations, SAPS Crime Administration System data generally includes details on weapons used and can be used to map gun crime more precisely. areas and districts, and stations where firearm crime is most concentrated. Docket quality, data collection, recording, mapping and analysis on all crimes related to firearms and ammunition should be improved. Dedicated firearm crime reduction units with adequate intelligence support should be established. Their key performance measure must be a reduction in murders, attempted murders and robberies involving firearms. Police measures to reduce firearm crime must be aligned with efforts to lessen the overall problem of firearm proliferation in South Africa.

Pretoria, South Africa: Institute for Security Studies, 2024. 16p.

By Gary Klein

In light of the difficulty achieving consensus about gun violence prevention at the federal level in the current political climate, leadership and innovation on gun violence prevention must come at the state and local levels. State legislators, law enforcement leaders, and state attorneys general must take the lead to find the pathway that most effectively protects their residents in collaboration with concerned communities. There is substantial evidence that states with comprehensive and effective gun laws have fewer incidents of gun homicides, gun suicides, and unintentional shooting deaths. These 50 proposals for state or local action have demonstrated success where they have been enacted and are a starting point for states interested in promoting public safety by addressing preventable gun violence.  

Washington, DC: Violence Policy Center, 2022. 24p.

By The Violence Policy Center

Large capacity ammunition magazines are the common thread running through most mass shootings in the United States. Since 1980, there have been at least 106 mass shootings (three or more fatalities not including the shooter) where the shooter used large capacity ammunition magazines containing more than 10 rounds. A total of 959 people were killed in these shootings, and 1,309 were wounded. This number is likely a significant undercount of actual incidents as there is no consistent collection or reporting on this data. Even in many high-profile shootings, information on magazine capacity is neither released nor reported. The Violence Policy Center has compiled this list of incidents by analyzing news reports and follow-up investigative reports on mass shootings. Only shootings in which there is specific information that large capacity magazines were used are included.  ( This document was last updated on January 11, 2024.

Washington, DC: Violence Policy Center, 2024. 17p. 

By Public Safety Canada

Overall crime rates in Canada have been decreasing over the past several decades. Despite this, there has been a marked increase in recent crime trends involving gun and gang violence (GGV). For example, between 2013 and 2020, Canada experienced a 91% increase in firearm-related homicides. At Canada’s borders, the Canada Border Services Agency (CBSA) has reported an overall increase in firearms seizures over the last five years. GGV-related issues are complex, cross-jurisdictional and multi-sectoral. Given the nature of gang violence and the knowledge that organized crime groups are involved in a variety of criminal activities and illegal commodities, interventions must be comprehensive and include activities across the spectrum of prevention, intervention, and enforcement. While provinces and territories (PTs) are responsible for the administration of justice, including policing, in their jurisdictions, there is also a federal role for supporting a multi-faceted coordinated approach to address GGV. To respond to these increased crime trends, the Minister of Public Safety and Emergency Preparedness Canada was mandated to work with provincial, territorial and municipal counterparts to develop a strategy for the federal government to best support communities and law enforcement in their ongoing efforts to make it tougher for criminals to secure and use handguns and assault weapons and to reduce GGV in communities across Canada. From this, Budget 2018 committed funding over five years to establish the Initiative to Take Action Against Gun and Gang Violence (ITAAGGV). This horizontal initiative supports Public Safety Canada (PS) (as the lead agency), the CBSA, and the Royal Canadian Mounted Police (RCMP) with investments across three themes.

Ottawa: His Majesty the King in Right of Canada, as represented by the Ministers of Public Safety and Emergency Preparedness, 2023. 40p.

By The Coalition to Stop Gun Violence

Gun violence is an American public health crisis decades in the making. The latest Centers for Disease Control and Prevention (CDC) data show that 39,707 people, 86% of whom were male, lost their lives to gun violence in 2019. Gun death data are the most reliable type of gun violence data currently available -- but gun deaths are only the tip of the iceberg of gun violence. With this report, it is our mission to share the most accurate and up-to-date data related to gun deaths while we advocate for more and better data related to gun violence in all its forms. Ultimately, we strive to apply these data to create and implement life-saving policies and programs that will end the gun violence epidemic

Washington, DC: Educational Fund to Stop Gun Violence. 2021. 37p.

Joseph Blocher, Reva B. Siegel

Government regulates guns, it is widely assumed, because of the death and injuries guns can inflict. This standard account is radically incomplete—and in ways that dramatically skew constitutional analysis of gun rights. As we show in an account of the armed protesters who invaded the Michigan legislature in 2020, guns can be used not only to injure but also to intimidate. The government must regulate guns to prevent physical injuries and weapons threats in order to protect public safety and the public sphere on which a constitutional democracy depends.

For centuries the Anglo-American common law has regulated weapons not only to keep members of the polity free from physical harm, but also to enable government to protect their liberties against weapons threats and to preserve public peace and order. We show that this regulatory tradition grounds the understanding of the Second Amendment set forth in District of Columbia v. Heller, where Justice Antonin Scalia specifically invokes it as a basis for reasoning about government’s authority to regulate the right Heller recognized.

Today, a growing number of judges and Justices are ready to expand gun rights beyond Heller’s paradigmatic scene: a law-abiding citizen in his home defending his family from a criminal invader. But expanding gun rights beyond the home and into the public sphere presents questions concerning valued liberties and activities of other law-abiding citizens. Americans are increasingly wielding guns in public spaces, roused by persons they politically oppose or public decisions with which they disagree. This changing paradigm of gun use has been enabled by changes in the law and practice of public carry. As courts consider whether and how to extend constitutional protection to these changed practices of public carry, it is crucial that they adhere to the portions of Justice Scalia’s Heller decision that recognize government’s

“longstanding” interest in regulating weapons in public places.

We show how government’s interest in protecting public safety has evolved with changing forms of constitutional community and of weapons threats. And we show how this more robust understanding of public safety bears on a variety of weapons regulations both inside and outside of courts—in constitutional litigation, in enacting legislation, and in ensuring the evenhanded enforcement of gun laws. Recognizing that government regulates guns to prevent social as well as physical harms is a critical first step in building a constitutional democracy where citizens have equal claims to security and to the exercise of liberties, whether or not they are armed and however they may differ by race, sex, or viewpoint.

116 Northwestern University Law Review 139-201 (2021)