1999
April 20: Columbine High School, Jefferson County - Eric Harris, 18, and Dylan Klebold, 17, killed 12 students and one teacher and wounded 24 other people before committing suicide in the school library.
Nov. 19: Deming Middle School, Deming, N.M. - Victor Cordova, 12, shot and killed a 13-year-old classmate. He was sentenced to two years in juvenile detention.
2000
Feb. 29: Buell Elementary School, Mount Morris Township, Mich. - A 6-year-old boy, whose identity was not released, shot and killed 6-year-old playmate Kayla Rolland. He was not charged with a crime, but he was removed from his mother's custody.
May 26: Lake Worth Community Middle School, Lake Worth, Fla. - After being sent home for misbehaving, Nathaniel Brazill, 13, returned to school and killed teacher Barry Grunow. Brazill was sentenced to 28 years in prison.
2001
March 5: Santana High School, Santee, Calif. - In a San Diego suburb, Charles "Andy" Williams, 15, killed two classmates - a 14-year-old and a 17-year-old - and injured 13. He was sentenced in 2002 to at least 50 years in prison.
April 26: Gutenberg High School in Erfurt, Germany - Robert Steinhaeuser, 19, a recently expelled student, entered his former school and methodically killed 16 people, going room to room with a shotgun and a handgun, before committing suicide.
2003
April 24: Red Lion Area Junior High School, Red Lion, Pa. - James Sheets, 14, brought three handguns to school and killed principal Eugene Segro before fatally shooting himself in the cafeteria.
Sept. 24: Rocori High School, Cold Spring, Minn. - Jason McLaughlin, 15, shot and killed 17-year-old Aaron Rollins, and critically wounded another student, who died of his injuries two weeks later. McLaughlin, charged as an adult, was found guilty of murder and sentenced to life in prison.
2004
September: Beslan School No. 1, Beslan, Russia - On the first day of school in this southern Russian town, Chechen militants took more than 1,100 children, parents and staff hostage in the gym. After a three-day siege, 331 hostages died - including 186 children - during the explosions and gunfire that ended the standoff.
2005
March 21: Red Lake Senior High School, Red Lake, Minn. - Jeff Weise, 16, killed his grandfather and his grandfather's girlfriend before driving to Red Lake Senior High School and killing five students, a teacher and a security guard. Weise fired on police as they entered the building, then retreated and killed himself.
Nov. 8: Campbell County Comprehensive High School, Jacksboro, Tenn. - A 15-year-old student shot a principal and two assistant principals before a teacher wrestled his weapon away. Assistant principal Ken Bruce was killed.
2006
Aug. 30: Orange High School, Hillsborough, N.C. - Former student Alvaro Castillo, 19, was arrested after opening fire in the school's parking lot, wounding two. Police found Castillo's father murdered at his home.
Sept. 13: Dawson College, Montreal - Kimveer Gill, 25, opened fire, authorities said, killing one person and wounding 20 others. He was killed in a shootout with police.
Sept. 27: Platte Canyon High School, Bailey - Duane R. Morrison fatally shot 16-year-old Emily Keyes and then himself.
Sept. 29: Weston High School, Cazenovia, Wis. - A 15-year-old student fatally shot his principal.
