Columbine High School / Federal Bureau of Investigation.

On April 20, 1999, Eric Harris and Dylan Klebold, students at Columbine High School, Jefferson County, Littleton, Colorado, entered the school and began firing weapons and detonating explosive devices. Fifteen students and teachers were killed and twenty three were injured. Harris and Klebold were among the dead, having taken their own lives. They were armed with two sawed-off shotguns, one 9MM carbine, one Tech-9 machine pistol, and in excess of thirty improvised explosive devices. These two students were considered outcasts. They associated with a group who wore long black coats, combat boots and went by the name of "The Trench Coat Mafia."