Secret Service study: School shooters showed warning signs

Police and others are seen outside STEM School Highlands Ranch, a charter middle school in the Denver suburb of Highlands Ranch, Colo., after a shooting Tuesday, May 7, 2019. Authorities said seven were injured and two suspects were in custody. (AP Photo/David Zalubowski)

WASHINGTON — Most students who committed deadly school attacks over the past decade were badly bullied, had a history of disciplinary trouble and their behavior concerned others but was never reported, according to a U.S. Secret Service study.