Dylan Klebold, American mass murderer, responsible for the Columbine High School massacre (died 1999)

Eric David Harris and Dylan Bennet Klebold were American high school seniors and mass murderers who perpetrated the Columbine High School massacre at Columbine High School on April 20, 1999, in Columbine, Colorado. Harris and Klebold killed 13 students and one teacher and wounded 23 others. After killing most of their victims in the school's library, they died by suicide. At the time, it was the deadliest high school shooting in U.S. history.

On April 20, 1999, a school shooting and attempted bombing occurred at Columbine High School in Columbine, Colorado, United States. The perpetrators, twelfth-grade students Eric Harris and Dylan Klebold, murdered 13 students and one teacher; ten were killed in the school library, where Harris and Klebold subsequently died by suicide. Twenty additional people were injured by gunshots, and gunfire was exchanged several times with law enforcement with neither side being struck. Another three people were injured trying to escape. The Columbine massacre was the deadliest mass shooting at a K-12 school in U.S. history until December 2012. It is still considered one of the most infamous massacres in the United States, for inspiring many other school shootings and bombings; the word Columbine has since become a byword for modern school shootings. As of 2025, Columbine remains both the deadliest mass shooting and school shooting in Colorado, and one of the deadliest mass shootings in the United States.

September 11 is the 254th day of the year in the Gregorian calendar; 111 days remain until the end of the year.