COLORADO--Authorities said 18-year-old Karl Pierson was seeking revenge against a faculty member when he opened fire in a Colorado high school.
Pierson shot and killed on student before turning the gun on himself. He got in through a door that should have been locked, according to authorities.
“We know that the doorway on the north side that the murderer entered is supposed to be locked. Unfortunately, it rarely is because it is more convenient for people to come and go from that area and not have to be obstructed by a locked door,” said Arapahoe County Sheriff Grayson Robinson.
The Sheriff said Pierson bought a shotgun from a local retailer after passing a background check on December 6. He also said Pierson spent a week stocking up on ammunition before the shooting.