The Violence Project tracks common traits found in mass shooters, warning signs and how to stop them

Commonalities found among mass shooters

New research shows mass shooters have a lot in common, and there's hope that such findings could be used to help prevent future attacks. The Violence Project has studied every U.S. mass shooting since 1966, tracking 160 mass shooters who each killed four or more people in public places.

Nearly all of them are male and the average age is 34. Psychologist Jillian Peterson, co-founder of The Violence Project, joined "CBS This Morning" to discuss the common traits shared by many of the people who commit such crimes, including childhood trauma. She also noted the "social contagion" phenomenon, which appears to make gunmen more inclined to act soon after another shooting takes place.

"Perpetrators study other perpetrators and when one happens the most concerning amount of time is the week after," Peterson said. "People read about it online. They see the notoriety these people get." 

She says an identifiable personal crisis typically precedes a mass shooting: "In the days, weeks, or months before the shooting there's a marked change in behavior and it's typically a suicidal crisis. So, about 80% we could identify were actively suicidal before they did this. And these really are suicides, of essence. They're horrific but the shooter typically dies."

As "CBS This Morning"co-host Tony Dokoupil noted, that means eight out of 10 gave a warning, potentially allowing those close to the person a chance to step in if they know how to spot and how to respond to the warning signs.

"We can train people to be thinking about those signs of crisis and to also not only recognize them but know what to do with those warning signs, know how to report to, know what intervention strategies are in place," Peterson said.

The Violence Project also researched 200 would-be mass shooters who didn't follow through, shedding light on the crisis intervention techniques that have worked to thwart such tragedies from occurring.

"You do find a lot of stories of people who were thinking about doing this, were in a really dark place, had seen others do this, were getting radicalized online, were gathering weapons, but someone stepped in," Peterson said. "And what is kind of inspiring is oftentimes it doesn't take that much… certainly, long-term intervention takes a lot but just getting someone through that moment, it can just be someone stepping in and saying, 'Are you OK? Let's reach out.'"

Peterson believes that crisis intervention, de-escalation and suicide prevention techniques could not only help in those situations but are useful in general, especially when it comes to addressing mental health issues, which are often misunderstood.

"It's important that mental illness and violence — you're not more likely to commit violence if you're mentally ill. You're actually less likely," Peterson said. "You're more likely to be a victim."