Columbine High School massacre — school shooting at Columbine High School in Columbine, Colorado, United States on April 20, 1999
The deadliest U.S. K–12 school shooting until 2012, it reshaped school security policy and sparked lasting national debate on gun violence.
Key Facts
- People killed
- 13 students and 1 teacher murdered
- Injured by gunfire
- 20 people
- Perpetrators
- Eric Harris and Dylan Klebold, both died by suicide
- Date
- April 20, 1999
- Copycat attacks inspired
- More than 70 as of June 2025
- Permanent memorial opened
- September 2007
By the Numbers
Location
Cause → Event → Consequence
Seniors Eric Harris and Dylan Klebold spent roughly a year planning an attack intended primarily as a bombing. Their homemade pipe bombs and propane tank devices, planted in the school cafeteria, failed to detonate on April 20, 1999. Their motives remain uncertain, though the pair left behind journals and videos expressing grievances.
After the bombs failed, Harris and Klebold launched a firearms assault on Columbine High School in Columbine, Colorado, killing 13 students and 1 teacher, wounding 20 others by gunfire, and injuring 3 more during escape attempts. Police response was heavily criticized as too slow. The attack ended when both perpetrators died by suicide in the school library.
The massacre prompted introduction of the immediate action rapid deployment (IARD) tactic for active-shooter situations and drove widespread adoption of zero-tolerance school security policies. It ignited national debate over gun control, bullying, and media influences. The event has since inspired more than 70 copycat attacks, a phenomenon known as the Columbine effect.