On April 20, 1999, two teenage gunmen killed 13 people in a
shooting spree at Columbine High School in Littleton,
Colorado, south of Denver.

At approximately 11:19 a.m., Dylan Klebold, 17, and Eric Harris,
18, dressed in trench coats, began shooting students outside
the school before moving inside to continue their rampage. By
11:35 a.m., Klebold and Harris had killed 12 fellow students and
a teacher and wounded another 23 people. Shortly after noon,
the two teens turned their guns on themselves and died by
suicide
  .

The event prompted a national debate on gun control and school
safety, as well as a major investigation to determine what
motivated the teen gunmen. In the days immediately following
the shootings, it was speculated that Klebold and Harris
purposely chose jocks, minorities and Christians as their
victims.