http://theconversation.com/if-you-want-to-know-how-to-stop-school-shootings-ask-the-secret-service-92333

The team studied 37 school shootings involving 41 attackers that took place from December 1974 through May 2000. Data included investigative, school, court and mental health records. In addition, 10 school shooters were interviewed to gain their perspectives from “conceptualization to execution” of the attacks. A series of findings emerged