Sept. 27, 2006: A 53-year-old gunman takes six girls hostage at Platte Canyon High School in Bailey, Colo. The gunman uses the girls as human shields for hours before fatally wounding a 16-year-old and then killing himself.
Sept. 17, 2006: Five Duquesne University basketball players are injured in a campus shooting by two men after a dance.
Sept. 2, 2006: Douglas Pennington, 49, kills his two sons and himself while visiting Shepherd University in West Virginia.
Nov. 8, 2005: A high school freshman is arrested in the fatal shooting of an assistant principal and wounding of two other school administrators at Campbell County High School in eastern Tennessee.
March 21, 2005: A 16-year-old student shoots and kills five schoolmates, a teacher, and an unarmed guard at Red Lake High School on the Red Lake Indian Reservation in Minnesota before taking his own life.
Sept. 24, 2003: A 15-year-old student fatally shoots two fellow students at Rocori High School in Cold Spring, Minn.
April 24, 2003: A 14-year-old student shoots and kills the principal of Red Lion Area Junior High School in south-central Pennsylvania before killing himself.
Oct. 28, 2002: A student at the University of Arizona Nursing College kills three of his instructors before killing himself.
Jan. 16, 2002: A graduate student at the Appalachian School of Law shoots and kills the dean, a professor, and a student and wounds three other students.
March 5, 2001: A 15-year-old student kills two fellow students and wounds 13 others at Santana High School in Santee, Calif., in San Diego County.
Aug. 28, 2000: A graduate student at the University of Arkansas is found dead with his English professor in an apparent murder-suicide.
May 26, 2000: A 13-year-old student kills his English teacher on the last day of classes in Lake Worth, Fla., after the teacher refused to let him talk with two girls in his classroom.
March 10, 2000: Two students in Savannah, Ga., are killed by a 19-year-old student while leaving a dance sponsored by Beach High School.
Feb. 29, 2000: A 6-year-old boy shoots and kills a 6-year-old classmate at Buell Elementary School in Mount Morris Township, Mich.
Nov. 19, 1999: A 13-year-old girl is shot in the head by a 12-year-old boy in school at Deming, N.M.
April 20, 1999: Eric Harris, 18, and Dylan Klebold, 17, kill 12 students and a teacher and wound 23 others before killing themselves at Columbine High School in Littleton, Colo.
June 15, 1998: One teacher and one guidance counselor are wounded by a 14-year-old boy in a Richmond, Va., school hallway.
May 21, 1998: Two teenagers are killed and more than 20 people hurt when a teenage boy opens fire at a high school in Springfield, Ore., after killing his parents.
May 19, 1998: Three days before his graduation, an 18-year-old honor student opens fire at a high school in Fayetteville, Tenn., killing a classmate who was dating his ex-girlfriend.
April 24, 1998: A 15-year-old student opens fire at an eighth-grade dance in Edinboro, Pa., killing a science teacher.
March 24, 1998: Two boys, 11 and 13, fire on their Jonesboro, Ark., middle school from nearby woods, killing four girls and a teacher and wounding 10 others.
Dec. 15, 1997: Two students in Stamps, Ark., are wounded by a 14-year-old boy who was hiding in the woods when he shot the students as they stood in the parking lot.
Dec. 1, 1997: Three students are killed and five wounded by a 14-year-old student at Heath High School in West Paducah, Ky.