Arapahoe High gunman entered school through door that was supposed to be locked
On the morning of December 13, eighteen-year-old Karl Pierson gave no indication that anything was amiss, according to Arapahoe County Sheriff Grayson Robinson. He took the time to have a meal and go bowling by himself. Then, at around 12:30 p.m., he entered Arapahoe High School through a door that…