School Shooter Killed Self Within 2 Minutes: Sheriff Victim Claire Davis 'not doing well': father By Matt Cantor, Newser User Posted Dec 14, 2013 6:45 PM CST 65 comments Comments Police use a dog to do an initial search at the Highlands Ranch, Colo., home of the 18-year-old shooting suspect Karl Pierson. (AP Photo/Ed Andrieski) (Newser) – School shooting suspect Karl Pierson shot himself within a minute and 20 seconds of entering Arapahoe High School in Centennial, Colorado, county sheriff Grayson Robinson says. He reportedly shot himself during a confrontation with an officer. "I believe that that shooter took his life because he knew that he had been found," Robinson says, per CNN. Pierson's weapons included three explosives and a knife; his shotgun and ammunition were, according to the sheriff, purchased legally, CNN tweets. Pierson fired five times, the sheriff notes. That included a point-blank shot at 17-year-old Claire Davis, who was critically injured and, her father tells ABC7, is "not doing well." Robinson says Davis came out of surgery faring worse. CNN adds that molotov cocktails were found in the school; one was burning when investigators entered. Pierson was reportedly targeting the school's debate coach.