Minnesota-made tool tracks the how and why behind mass shootings

All but 2 percent of mass shooters were men, according to national database

Researchers James Densley and Jillian Peterson stand for a portrait
Researchers James Densley and Jillian Peterson stand for a portrait at Hamline University in St. Paul on March 19, 2019. Densey and Peterson are co-founders of The Violence Project, a research and training organization with the mission of reducing violence in society.
Evan Frost | MPR News file

A new database launched by Twin Cities researchers aims to help policymakers and the public understand the conditions that contribute to mass shooting incidents in the United States.

Researchers with the nonpartisan Violence Project documented characteristics associated with 171 people who committed mass shootings, which was defined as shooting and killing four or more people in a public space like a house of worship or school. The database went online Tuesday.

Metropolitan State University criminal justice professor and Violence Project co-founder James Densley said researchers looked at factors in the shooters' lives, including mental health issues, whether they had suicidal thoughts and how they had access to guns.

"For a start, we need to be a little bit more attuned to the fact that people are in crisis, and are looking for help, and perhaps aren't getting it," Densley said.

Researchers found that 98 percent of mass shooters were men and that 52 percent were white. The proportion of mass shooters who had been diagnosed with mental health conditions was only slightly higher than the general population, according to researchers.

About 77 percent of mass shooters purchased some of their firearms legally. Almost half the shooters leaked their plans in advance, and 1 in 5 mass shooters studied other mass shooting incidents.

Mass shootings have claimed more than 1,200 lives in the last half century, according to the report. The number of shootings and number of victims has been gradually increasing, Densley said.

"We're just fed up with switching on the news and hearing about another mass shooting in our community and another community that's shattered by that,” Densley said.”I think it’s time to move into action.”

The database aims to inform policies that could prevent future mass shooting incidents, according to Jillian Peterson, an assistant professor of criminology and criminal justice at Hamline University and co-founder of the Violence Project.

“Mass shootings are a complex issue, requiring multiple avenues of prevention,” Peterson said in a statement. “The goal of this project is to ground our public policy discussions in data and develop evidence-based policies to prevent these tragedies.”

The database was created with the support of the National Institute of Justice.

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