Aug. 1, 1966: Charles Whitman points a rifle from the observation deck of the University of Texas at Austin's Tower and begins shooting in a homicidal rampage that goes on for 96 minutes. Sixteen people are killed, 31 wounded.
May 4, 1970: Four students are killed and nine wounded by National Guard troops called in to quell anti-war protests on the campus of Kent State University in Ohio.
July 12, 1976: Edward Charles Allaway, a 37-year-old janitor at California State University, Fullerton, walked into the library with a .22-caliber rifle and killed seven people, wounding two others. Found innocent by reason of insanity, he has been held in a mental institution ever since.
Nov. 1, 1991: Gang Lu, 28, a graduate student in physics from China, reportedly upset because he was passed over for an academic honor, opens fire in two buildings on the University of Iowa campus. Five University employees are killed, including four members of the physics department, one other person was wounded. The student fatally shoots himself.
Aug. 15, 1996: Frederick Martin Davidson, 36, a graduate engineering student at San Diego State, is defending his thesis before a faculty committee when he pulls out a handgun and kills three professors.
Sept. 17, 1996: 19-year-old Jillian Robbins killed one student and wounded four others with a sniper rifle on the HUB-Robeson Center lawn at Penn State, before being subdued. Claiming to have been suicidal, Robbins plead guilty to third-degree murder and four counts of attempted murder in 1998, and was sentenced to 30-to-60 years in prison.
October 1997: Sixteen-year-old boy stabs mother, then shoots dead two students at school in Mississippi, injuring several others
December 1997: Fourteen-year-old boy kills three students in Kentucky
March 1998: Two boys, 11 and 13, kill four girls and a teacher in Arkansas
April 1998: Fourteen-year-old shoots dead a teacher and wounds two students in Pennsylvania
May 1998: Fifteen-year-old boy shoots himself in the head after taking a girl hostage
May 1998: Fifteen-year-old shoots dead two students in school cafeteria in Oregon
June 1998: Two adults hurt in shooting by teenage student at high school in Virginia
April 1999: Two teenagers shoot dead 12 students and a teacher before killing themselves at Columbine School in Colorado
May 1999: Student injures six pupils in shoot-out in Georgia
November 1999: Thirteen-year-old girl shot dead by a classmate in New Mexico
February 2000: Six-year-old girl shot dead by classmate in Michigan
Aug. 28, 2000: James Easton Kelly, 36, a University of Arkansas graduate student recently dropped from a doctoral program after a decade of study and John Locke, 67, the English professor overseeing his coursework, are shot to death in an apparent murder-suicide.
March 2001: Pupil opens fire at a school in California, killing two students
Jan. 16, 2002: Graduate student Peter Odighizuwa, 42, recently dismissed from Virginia's Appalachian School of Law, returns to campus and kills the dean, a professor and a student before being tackled by students. The attack also wounds three female students.
Oct. 28, 2002: Failing University of Arizona Nursing College student and Gulf War veteran Robert Flores, 40, walks into an instructor's office and fatally shoots her. A few minutes later, armed with five guns, he enters one of his nursing classrooms and kills two more of his instructors before fatally shooting himself.
April 2003: Teenager shoots dead head-teacher at a Pennsylvania school, then kills himself
May 9, 2003: Clad in camouflage, Biswanath Halder, 62, a business school alumnus of Case Western Reserve University in Cleveland, Ohio, killed one student and injured two other people during a seven-hour standoff. Almost a hundred people were trapped inside as Halder wandered the halls, firing hundreds of rounds of ammunition, searching for an employee he had sued. He was convicted and sentenced to life in prison.
May 2004: Four people injured in shooting at a school in Maryland
March 2005: Minnesota schoolboy kills nine, then shoots himself
November 2005: Student in Tennessee shoots dead an assistant principal and wounds two other administrators
Sept. 2, 2006: Douglas W. Pennington, 49, kills himself and his two sons, Logan P. Pennington, 26, and Benjamin M. Pennington, 24, during a visit to the campus of Shepherd University in Shepherdstown, West Virginia. His sons were seniors at the university.
September 2006: Gunman in Colorado shoots and fatally wounds a teenage schoolgirl, then kills himself; two days later a teenager kills the head teacher of a school in Cazenovia, Wisconsin
October 2006: A 32-year-old gunman shoots dead at least five girls at an Amish school in Pennsylvania, before killing himself
April 2, 2007: A man and a woman were shot to death in the University of Washington's architecture building in an apparent murder-suicide. The female victim, a 25-year-old university employee, had a restraining order against the man, who "almost certainly" shot her and took his own life, according to university police.
April 16, 2007: A gunman kills 32 people in a dorm and a classroom at Virginia Tech in Blacksburg, Virginia. The gunman himself later dies.
October 2007: A teenage gunman reportedly shoots and wounds five people at a high school in Cleveland, Ohio, before killing himself.
February 8, 2008, Three dead in Louisiana campus shooting, A nursing student shot two women to death and killed herself in front of horrified classmates at a college in the southern U.S. state of Louisiana
February 14, 2008, Northern Illinois University shooting leaves 6 dead, 16 wounded, A former graduate student armed with a shotgun and two handguns opened fire in a lecture hall at Northern Illinois University in DeKalb, killing five students and wounding 16 others before shooting himself to death.
Term "new normal" when discussing their state of mind in the wake of the hellish violence that shattered their lives on April 20, 1999. Twelve students and a teacher were killed that day and 23 others were wounded before their teenage assailants took their own lives.
It was one of the bloodiest episodes in U.S. history, and one of a dozen shootings in schools from Bethel, Alaska, to Conyers, Georgia, during an 18-month period.
The shootings aroused concerns about school safety and gun control, fears that were still very real for many Americans a year later. Just days before the one-year anniversary of the Columbine shooting, a Wall Street Journal-NBC News poll found that 70 percent of Americans believed such a shooting could occur at a school in their own community.