School shootingsSchool shooters usually show these signs of distress long before they open fire, our database shows

By Jillian Peterson and James Densley

Published 11 February 2019

Our initial analysis of the school shooting data found some noteworthy patterns. All mass school shooters since 1966 had a large number of risk factors for violence. Forty-five percent had witnessed or experienced childhood trauma, 77 percent had mental health concerns, as evidenced in a prior diagnosis, previous counseling or hospitalization, or medication use, and 75 percent had an interest in past shootings, as evidenced in their writing, social media posts or other activities. The majority of mass school shooters – 87 percent – showed signs of a crisis, as exhibited in their behavior, before the shooting. Seventy-eight percent revealed their plans ahead of time, often on social media. As juveniles, they also used guns that they stole from parents, caregivers and other significant adults in their lives. Our analysis found that about 80 percent of mass school shooters were suicidal. These findings make it clearer why current strategies are inadequate.

Two years before he lined his schoolmates up against a classroom wall and executed them one by one, the student, who would become the gunman, tried to show his English teacher something important.

He had quietly slid up his sleeves to reveal the cut marks running down his arms. The teacher panicked. A novice educator at the time, she had never been coached or trained in what to do in these situations, what to say or how to help. So she passed the student off to another teacher, who then filed a form with the principal’s office. She felt fairly certain nothing else came of it.

“He was asking for help,” the teacher said in reflecting on the encounter during a recent interview. “If I’d had some training to help him, a five-step sheet to follow, say this, say that, maybe I could have made a difference?”

The story is one of dozens that we have collected over the past two years in our effort toward studying the life histories of mass shooters. It typifies what we believe is one of the biggest challenges that schools face when it comes to averting school shootings – and that is recognizing and acting upon warning signs that school shooters almost always give well before they open fire.

We are both criminologists who study aggression and violence. One of us focuses on mental illness among offenders. The other has an extensive background in group violence.

Together, we have built a database of the 160 mass public shootings that have taken place in the United States since 1966 for a project funded by the National Institute of Justice, the research arm of the U.S. Department of Justice. For mass public shootings, we use the common definition of an event in which four or more victims are killed with a gun in a public place.