An explanation still hasn't emerged for why a man killed 26 people at Sandy Hook Elementary School, but it does appear that he attended the school as a youngster, Connecticut Gov. Dan Malloy told NBC News on Sunday. Adam Lanza, 20, shot his mother multiple times in the head in her home before driving to the school in her car and killing 20 children and six adults in two classrooms Friday in Newtown, Conn., authorities said Sunday. The gunman then shot himself in the head as emergency crews arrived at the scene.