A shooter opens fire at a school or in an office, unleashing grief — and difficult questions. Soon after the hail of bullets comes a barrage of theories about what caused the killings and what could have been done to prevent them.

Now a group of Minnesota researchers is introducing new data for the discourse with the creation of a “Mass Shooter Database” bolstered by $300,000 in federal funding.

Hamline University Prof. Jillian Peterson, Metropolitan State University Prof. James Densley and a team of students researched and coded data for every mass shooter in the United States since Charles Whitman climbed a tower at the University of Texas in 1966 and killed 14 people, an event often considered the first modern-era televised mass shooting.

Since then there have been 171 mass shooters, according to the federal government’s definition, killing 1,239 people.

Peterson, who’s a psychologist, and Densley, a sociologist, are creating the database as part of the Violence Project, their nonpartisan think tank. They have used court records, witness accounts, interviews and media reports to collect more than 100 data points on each of the 171 mass shooters.

The Violence Project database will be released next week to other researchers, policymakers and the public. But its work is already receiving international media attention.

“The goal is to present the data to break down the myths,” Peterson said.

The data points touch on the shooters’ history of mental illness, their criminal behavior, employment record, how they obtained their weapons and what they communicated before the incident — even the order they were born in their families.

“Let’s draft policies and solution on data, vs. just emotions,” said Peterson, an assistant criminology professor and director of Hamline’s Center for Justice and Law.

She said the project started out as a spreadsheet but really took off after Stephen Paddock opened fire on a Las Vegas country music festival in 2017, killing 58 people and wounding more than 400.

“We just felt dissatisfied with the level of discourse and the level of knowledge about mass shootings,” Densley said. “People on the left would automatically say it’s a gun issue. People on the right would say this is a mental illness issue.”

Included in their database are two Minnesota tragedies. In March 2005, 16-year-old Jeffrey Weise shot and killed nine people at a school and a home on the Red Lake Indian Reservation before taking his own life. In September 2012, Andrew Engeldinger, angered over losing his job, shot and killed five people at Accent Signage Systems in Minneapolis. The latter incident became the deadliest workplace shooting in Minnesota history.

What the data show

Densley compares their work to research started several years ago and led by the Washington Post to track the number of individuals killed by police in the United States, using news accounts and publicly available data.

“We see our work as another example of that,” he said. “We are putting together the information that is out there, that is accessible and digestible. This moves us forward to say, ‘What do we actually know about mass shootings? What does the data tell us?’ ”

The Violence Project is one of three research projects focused on mass shootings to receive funding from the National Institute of Justice, an arm of the U.S. Department of Justice. Federal authorities define a mass shooting event as four or more people killed in a public space, excluding gang and family violence.

Peterson and Densley’s researchers wrote letters to 35 surviving mass shooters (most die at the scene) now in prisons across the country. Five agreed to sit for interviews, Peterson said.

“We asked them, ‘Is there anything or anyone that could have stopped you?’ They all say yes. They recognized they were in crisis,” Peterson said.

Densley, a professor in Metro State’s School of Law Enforcement and Criminal Justice, said they’ve just started to delve deep into their own data, looking for commonalities. He said they’ve made some early findings.

For instance, nearly all the shooters shared four traits: early childhood trauma and/or exposure to violence at a young age; an identifiable grievance or crisis point; finding validation for their violent belief system, including study of past shootings; and the means to carry out an attack, including access to firearms.

When a mass shooting occurs, many quickly assume it’s a mental health issue. “But we see crimes driven by interpersonal conflicts, problems in the workplace or a hateful ideology,” Densley said. “If we put all the eggs in the mental health basket, we will miss that part of the data.”

While school shooters who target children tend to grab the most media attention, Peterson said the biggest increase in the past five years has been in restaurant and retail mass shootings.

The data belie the “they just snapped” narrative that often comes out in the days after a mass shooting, as reporters interview neighbors and other acquaintances with limited insight into the shooter’s life, said Kyle Knapp, a student researcher and Hennepin County probation officer.

“The perception is that shooters are the quiet guy in the office or school, but then they snapped,” Knapp said.

But a number of them had prior criminal histories and many were in crisis, resulting in a marked change in behavior before the shootings.

“We see these as opportunities for intervention,” Densley said. “What can we be doing in our workplaces, schools and communities to be providing resources and outreach to people in crisis?”

Breaking down the data

Densley said that the great majority of mass shooters get their guns legally. Most school shooters took them, unsecured, from parents or grandparents.

“We still see examples where the existing legal system may have failed — individuals who have histories of domestic violence or criminal history that should have excluded them from getting firearms,” he said.

Project researchers said they’re finding commonalities when they break down data into subgroups based on the shooters’ targets, including high schools, workplaces, houses of worship, colleges, retail stores and restaurants.

Peterson said she’s spent time analyzing 13 high school shooters and has also looked at 57 school shooters with fewer than four victims. Of some 70 planned and executed school shootings, she found that none of the school shooters had figured out an escape route.

“It’s all suicides. Most were actively suicidal before the shooting,” she said.

Nearly 80% of the shooters leaked their deadly plans to others beforehand. More than 90% were current or former students, which should make schools and policymakers reevaluate the value of active shooter drills, Peterson said.

“Lock down drills and active shooter drills — none of that makes sense if the perpetrator is running through those drills too,” she said.

Zero-tolerance, punitive strategies where troubled teens are suspended or expelled, also may not make sense or mitigate the threat. A punitive approach may make friends and family members less likely to tell authorities or school officials about a possible threat.

“We hope this data opens these windows of conversation again,” Densley said. “We could be preventing mass shootings, and that is our goal.”