The U.S. Secret Service Safe School Initiative found these common characteristics among the 41 school shooters involved in 37 school shootings between 1974 and 2000.

• In nearly every incident, the attacker developed the violent idea and planned the attack.

• More than half the attackers had revenge as a motive.

• The attackers had a range of friendship patterns from socially isolated to popular.

• Few of the attackers were diagnosed with a mental disorder prior to the incident.

• The attackers had a range of behavioral histories from no observable problems to multiple problems warranting reprimand and/or disciplinary actions.

• In nearly every incident, the attackers had difficulty coping with a major change in a significant relationship or a loss of social status prior to the school shooting.

• In most incidents, the attackers got the guns from home or that of a relative.

• An adult such as a school administrator or teacher was often concerned about the attacker’s behavior prior to the incident.

Source: "Interim Report on the Prevention of Targeted Violence in Schools," October 2000, U.S. Secret Service National Threat Assessment Center.