Photos: Deadliest school shootings in U.S.
April 20, 1999: Columbine High School April 20, 1999: Students Eric Harris, 18, and Dylan Klebold, 17, opened fire at Columbine High School in Littleton, Colo., killing 12 classmates and a teacher and wounding 26 others before killing themselves in the school's library. Pictured: Students from Columbine High School watch as the last of their fellow students are evacuated from the school building, April 20, 1999 following the shooting spree at the school. Credit: MARK LEFFINGWELL/AFP/Getty Images
Other Slideshows
Photos: Parts of St. Louis area flooded after storms
Photos: Shark attack off Texas beach
Photos: St. Louis Zoo debuts baby lemurs
Photos: Pope Francis blesses Harley-Davidsons
Photos: Four-legged Spurs fans show their pride
Photos: Erin Brady, of Connecticut, wins Miss USA
