On April 20, 1999, the worst incidence of school violence in U.S. history occurred at Columbine High School in Littleton, Colorado. Two heavily armed students, Eric Harris and Dylan Klebold, killed 13 people and wounded 23 before taking their own lives.
If you know about a weapon threat at school, don’t delay — tell an adult you trust or call the toll-free number 1 (866) SPEAK UP, a nationwide anonymous hotline operated by the anti-gun violence group PAX.
See photos from anniversary memorials of the Columbine High School shootings and remember to call to report a weapons threat.
Sources: American Psychological Association, Focus Adolescent Services
This is an aerial view of Columbine High School. The school has been modified since the shootings, with a new library replacing the room where 10 students were killed.
Anne Marie Hochhalter, who was paralyzed from her wounds inflicted by the shooters, speaks at the memorial service held on the five-year anniversary of the tragedy. Dylan Klebold and Eric Harris killed 13 people and wounded 23.
Students bow their heads in prayer during the memorial service. The service and a candlelight vigil were held in Clement Park, a sprawling expanse of green that nearly surrounds Columbine High School.
A woman cries during the memorial service. A psychologist in charge of counseling for Columbine victims said that a fifth anniversary, "puts people back to dealing with something that they have been walling off."
Family members wear special shirts and carry balloons to the service in memory of Kyle Velasquez, a student who was killed in the shootings.
In tribute to the victims of the tragedy, Air Force planes fly over the service in a missing man formation.