One-third of the attackers who terrorized schools, houses of worship or businesses nationwide last year had a history of serious domestic violence, two-thirds had mental health issues, and nearly all had made threatening or concerning communications that worried others before they struck, according to a U.S. Secret Service report on mass attacks.

The Secret Service studied 27 incidents where a total of 91 people were killed and 107 more injured in public spaces in 2018. Among them: the shooting at Marjory Stoneman Douglas High School in Parkland, Florida, were 17 people were killed and 17 others injured, and the fatal attack at the Tree of Life Synagogue in Pittsburgh.

The report analyzed the timing, weapons, locations and stressors of the attacker, plus events that led up to the incident, in an effort to better understand how such attacks unfold and how to prevent them. Members of the Secret Service National Threat Assessment Center, which did the study, briefed police, public safety and school officials at a seminar Tuesday.

“We want the community to know prevention is everyone’s responsibility,” said Lina Alathari, the center’s chief. “Not just law enforcement.”

Other incidents examined included a man who drove a truck into a Planned Parenthood clinic in New Jersey, injuring three, and a man who killed two at a law firm, and then one at a psychologist’s office in June. Criteria for the study included an incident where three or more people were injured in a public place.

Most attackers were male, ranging in age from 15 to 64. The domestic violence history often included serious violence. While 67% had mental health issues, only 44% had a diagnosis or known treatment for the issue.

Most of the attacks occurred midweek. Only one was on a Saturday. As for motive, more than half of the attackers had a grievance against a spouse or family member, or a personal or workplace dispute. Also, 22% had no known motive. In nearly half the cases, the attacker apparently selected the target in advance.

Alathari and her colleagues want communities to be aware of concerning behavior and these trends so officials have something to look out for.

The Secret Service center is tasked with researching, training and sharing information on the prevention of targeted violence, using the agency’s knowledge gleaned from years of watching possible targets that may or may not be out to assassinate the president.

Alathari said her team is working on a new report on school shootings and how to prevent them, and investigating averted attacks to try to figure out why someone didn’t follow through.

“There is not a single solution,” Alathari said. “The more that we’re out there, training, the more we’re out there with the community … the more we share information … I think it will help really alleviate and hopefully prevent even one incident from happening. One is too many.”

(AP)