Photos: Remembering Columbine Police stand outside the east entrance of Columbine High shool as bomb squads and SWAT teams secure students 20 April 1999 in Littleton, Colorado, after two masked teens on a "suicide mission" stormed the school and blasted fellow students with guns and explosives before turning the weapons on themselves. Police fear at least 25 people were killed. (Mark Leffingwell/Getty Images)