(David Goldman | AP file photo) In this Dec. 16, 2012 file photo, people arrive on a school bus at Newtown High School for a memorial vigil attended by President Barack Obama for the victims of the Sandy Hook Elementary School shooting, in Newtown, Conn. Most of the students who commit deadly school attacks were bullied, had a history of disciplinary trouble and their behavior concerned others, but it wasn’t reported. That’s according to a comprehensive study by the U.S. Secret Service’s National Threat Assessment Center of 41 school attacks since the 1999 Columbine High School Shooting.