On April 20th, 1999, at the Columbine High School in Colorado, Eric Harris and Dylan Klebold, shot to death 12 students, one teacher, and themselves. Twenty-one others were wounded by them, and additional individuals were wounded while escaping the massacre. Columbine . They also injured 21 other students directly, and three people were injured while attempting to escape. Columbine currently ranks as the fourth deadliest school massacre, but it remains the deadliest event of its kind in the US. (The three deadlier massacres were very different in numerous ways and should not be placed on the same scale. As a US K-12, shootings by students event, Columbine stands alone.)
The documentary Bowling for Columbine does a good job of placing this event in the broader context of gun regulation in North America.
Utterly insensitive, armed and dangerous gun rights advocates have often used Columbine as a place to make their case that guns should always be unregulated. The latest is the series of pro-gun rallies held on Monday.