The suspects were either current or former students.
>> Aniah Blanchard search: Ibraheem Yazeed wanted on suspicion of kidnapping, search continues
The report said all cases had opportunities to intervene before the attacks happened.
"The goal of this process is to intervene before an attack can occur," U.S. Secret Service Director James Murray said.
The report said most attackers used guns or knives often taken from the home.
Most had a history of mental health challenges and all of the attackers had at least one social stressor such as bullying or a romantic break-up.
>> Mormon family slaying: First funerals held for 9 relatives killed in northern Mexico
Parents of the victims of the 2018 Parkland, Florida mass shooting at Marjorie Stoneman Douglas High School joined Murray and his team in announcing the findings.
"Our nation must learn that the best way to stop a school shooting is to prevent it,” Tony Montalto, father of a Parkland shooting victim, said.
The research is meant to help school and law enforcement officials better identify and respond to the warning signs.
The report did not include incidents related to gang or drug violence.
About the Author