William Paterson University

New research led by William Paterson University Associate Professor of Criminal Justice Jason R. Silva finds that perpetrators communicated violent intentions through leakage or threats before 41 percent of 483 U.S. mass shootings he examined – shootings that occurred between 2000 and 2023 that left four or more victims dead – and that, among shootings preceded by these warning signs, the warning signs were not reported before the attack in nearly half of cases.

Published September 14 in the American Journal of Criminal Justice, the study is Silva’s first of five planned publications stemming from a $524,000 National Institute of Justice grant to William Paterson University to advance research on mass shooter leakage and threats. Silva serves as principal investigator for the project.

In collaboration with Professor Adam Lankford of the University of Alabama, Silva reviewed existing databases, official records, and news reports to assess more than 30 factors related to warning signs and how people responded. The researchers distinguished between “leakage”—communicating violent intentions to third parties, such as friends, family members, or an online audience—and threats made directly to potential victims.

“One of the most important questions in mass shooting prevention is not simply whether warning signs occur, but whether other people recognize them and what happens next,” Silva explains. “We wanted to understand when perpetrators communicate their intentions, who receives those warning signs, and what factors make reporting and intervention more likely.”

In their resulting article, titled “A Comprehensive Assessment of Leakage, Threats, Public Reporting, and Responses to Reports among Public, Family, and Felony Mass Shootings,” Silva and Lankford found that leakage or threats were particularly common before public mass shootings—those involving victims largely chosen at random or for their symbolic value. Seventy-one percent of public mass shootings were preceded by such warning signs, compared with 37 percent of family mass shootings.

The researchers also identified a significant gap between warning signs becoming known and those signs being reported. Among the 197 mass shootings preceded by leakage or threats, members of the public reported those warning signs before the attack in 54 percent of cases.

“What stood out most was that even when leakage or threats occurred, they did not always lead to a report,” Silva says. “People may be uncertain whether concerning behavior is serious enough to report. Our findings suggest that prevention efforts should make it easier for people to come forward, even when they are uncertain whether someone will actually carry out a threat.”

Reporting occurred more frequently when warning signs were clearer—for example, when perpetrators directly threatened potential victims, specifically expressed an interest in committing mass violence, or communicated warning signs in multiple ways or to multiple people.

To improve reporting, the researchers recommend that authorities educate the public about warning signs, encourage people to report concerning communications even when they are unsure whether someone will act on them, and make it easier to submit reports anonymously. They also emphasize building public trust in law enforcement and the justice system.

Silva, who developed the Global Mass Shooting Database to better understand and compare perpetrator motivations and identify strategies for intervention and prevention, focuses his broader research on mass shootings, school violence, terrorism, and media coverage of crime.

The second of Silva’s planned articles supported by the National Institute of Justice grant is forthcoming in the Journal of Interpersonal Violence. It examines factors associated with the successful prevention of public mass shooting plots.