FBI Exclusive: Inside the mind of a mass shooter

After each tragic mass shooting in the United States, the same questions are asked: why did it happen and could it have been prevented?

Boston 25 News Washington correspondent Blair Miller had rare access inside the FBI unit where agents are trying to get inside the mind of mass shooters, to answer those questions and stop the next tragedy.

The Columbine High School shooting in Colorado in 1999 was one of their earliest case studies.

Salli Garrigan was a junior at Columbine that year.

“I remember it through senses. I always say senses. Sometimes I'll hear something and my memory will pop up right away. Of something I hear," Garrigan recalled with Miller.

She lost 12 classmates that day, in what was the deadliest school shooting in history at the time. The FBI meticulously studied the suspects, as it does with all mass shootings.

Two decades and hundreds of cases later, the FBI now has a Behavioral Threat Assessment Center, focusing on ways to see inside the minds of those who cause such extreme violence.

“We focus on the behaviors... all the things that are going on with that individual person and what is driving them toward that decision,” said the FBI’s John Wyman.

The unit recently looked in-depth at 63 different active shooter cases and found, while there's no "profile" of a terrorist or a shooter, there are similarities.

"On average, each person had 3.6 stressors in the year prior," Wyman said.

Those stressors are something that causes deep internal tension, like mental health concerns, personal loss, financial strain, or losing a job.

“That's difficult for the public to understand,” Wyman explained. “People want a clear example of 'this is why somebody did it' and most of the time, it's not just one clear thing.”

The FBI also studies the haunting details of the planning that goes into causing such violence.

“Sometimes people will spend years planning for a potential attack.  At Columbine, there was that extensive planning,” said Wyman.

Garrigan is now 36 with two of her own kids and still struggles to understand.

“What makes you angry?” Miller asked. “At 20 years these continue to happen,” Garrigan replied.  “If you really want to make change, let's make change and let's chip away and make it a little bit harder for people to obtain a gun.”

The FBI couldn't tell us how many attacks they've prevented with their research, only that it “happens often."