— March 5, 2001: Charles "Andy" Williams, 15, killed two fellow students and wounded 13 others at Santana High School in Santee, Calif.
— April 20, 1999: Students Eric Harris, 18, and Dylan Klebold, 17, opened fire at Columbine High School in Littleton, Colo., killing 12 classmates and a teacher and wounding 26 others before killing themselves in the school's library.
— May 21, 1998: Two teenagers were killed and more than 20 people hurt when Kip Kinkel, 17, opened fire at a high school in Springfield, Ore., after killing his parents.
— March 24, 1998: Andrew Golden, 11, and Mitchell Johnson, 13, killed four girls and a teacher at a Jonesboro, Ark., middle school. Ten others were wounded in the shooting.
— Dec. 1, 1997: Three students were killed and five wounded at a high school in West Paducah, Ky. Michael Carneal, then 14, later pleaded guilty but mentally ill to murder and is serving life in prison.
— Oct. 1, 1997: Luke Woodham, 16, of Pearl, Miss., fatally shot two students and wounded seven others after stabbing his mother to death. He was sentenced the following year to three life sentences.