Centennial, Colorado

18-year-old Karl Pierson, shot 17-year-old student Claire Davis in the head, fatally injuring her, in a hallway in Arapahoe High School. Pierson then took his own life. Pierson was armed with a shotgun, three Molotov cocktails, and a machete. His intention was to shoot the librarian who had disciplined him. Claire Davis died from her injuries on December 21, 2013.