CNN Editorial Research (CNN) — Here is some background information about the deaths of 14 people at Columbine High School in Littleton, Colorado, on April 20, 1999. Facts Twelve students and one teacher were killed by students Dylan Klebold, 17, and Eric Harris, 18, in the initial attack. In 2025, the death of an injured student at the time was classified as a homicide, bringing the death toll to 14. The pair made home videos prior to the attack…