The gunman who opened fire at a Colorado high school on December 13 was found to have entered an unlocked door. The door is supposed to be locked at all times but rarely is according to the principal.
The gunman entered without an obstruction. He had legally bought a shot gun a week before and had spent the last week stocking up on ammo.
Authorities identified the gunman as 18-year-old Karl Pierson, who was a student at the high school.
Pierson fatally wounded 17-year-old Claire Davis before turning the gun on himself. The attack was less than one minute and twenty seconds before the young man turned the gun on himself.
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