BENTON, Ky. — A 15-year-old student killed two classmates and hit a dozen others with gunfire Tuesday, methodically firing a handgun inside a crowded atrium at his rural Kentucky high school."He was determined. He knew what he was doing," said Alexandria Caporali, who grabbed her stunned friend and ran into a classroom as their classmates hit the floor."It was one right after another -- bang bang bang bang bang," she added. "You could see his arm jerking as he was pulling the trigger."He kept firing, she said, until he ran out of ammunition and took off running, trying to get away.