Jefferson County Sheriff's Department / AP
Eric Harris, left, and Dylan Klebold, carrying a TEC-9 semi-automatic pistol, are pictured in the cafeteria at Columbine High School, in Littleton, Colo., during their April 20, 1999, shooting rampage where they killed a teacher and 12 students. Both gunmen later killed themselves in the school library.
KCNC-TV / AP
In this image taken from TV, a student is rescued by emergency personnel during the shooting spree at the school in the southwest Denver suburb.
George Kochaniec Jr. / Rocky Mountain News via Newscom
Columbine High School students at the triage scene.
Eric Gay / AP
An unidentified woman looks at 15 crosses on a hill above the school in Littleton, Colo. -- one cross for each of the people who died during the shooting rampage, including the two gunmen.
Rick Wilking / AFP
A woman cries after writing on a casket containing the body of Rachel Scott at funeral services in Littleton on April 24, 1999. Scott was one of the 12 students who died in the attack.
Eric Gay / AFP/Getty Images
Columbine students embrace as they enter the high school after a "take back the school" rally Aug. 16, 1999. With cheers and words of hope, nearly 2,000 students, many wearing T-shirts declaring "We are Columbine," returned to school for the first time since the deadly rampage.
Linda McConnell / The Rocky Mountain News via Newscom
Five months after the attack, Pat Ireland does physical therapy with Brain Trzaskos, RPT, at Craig Hospital in Denver. Ireland gained fame as "the boy in the window" after he made a life-saving plunge out of the school library. Shot twice in the head and once in the foot, Ireland landed in the arms of Lakewood SWAT team rescuers.
Marc Piscotty / Rocky Mountain News via Newscom
Columbine shooting victim Valeen Schnurr acknowledges the cheers as she leaves the stage -- diploma in hand -- during graduation ceremonies the year after the attack.
Ed Andrieski / AP
Roger Kovacs and his wife, Lesli, visit a memorial at Chapel Hill Memorial Gardens in Littleton on April 20, 2007, the eighth anniversary of the massacre.