DENVER (AP) — A student who killed a classmate before taking his own life at a suburban Denver high school last year showed a friend photos of the Sandy Hook Elementary shooting and thought one of the images was "funny in a crude way," according to documents released Thursday.
Karl Pierson, 18, also showed the friend pictures of the shotgun he later used in the Dec. 13 attack at Arapahoe High School, according to investigators' applications for search warrants.
The Arapahoe County Sheriff's Office released the records to The Associated Press as part of an open-records request. The documents show detectives investigated tips that other students knew of Pierson's plan, but police have said they concluded no one else was aware of it.
Authorities believe Pierson was targeting his debate coach when he entered the school with a shotgun, machete, homemade bombs and 125 rounds of ammunition. Investigators said he shot and killed 17-year-old Claire Davis before turning the gun on himself in the school library as security officers closed in. The coach escaped unharmed.
The documents show Pierson had written numbers on his arm corresponding to classrooms and the message, in Latin, "The die has been cast."
Two school security guards told investigators they saw Pierson looking at pictures of guns and mass shootings on his computer six weeks before the shooting. And police found a book about the Columbine High School attack when they searched his mother's home.
An autopsy report showed the only substance in Pierson's system the day he died was caffeine.
In closing the case last week, Sheriff Dave Walcher said school officials did not suspend Pierson in September and allowed him to return to class after he threatened to kill the coach, who had recently demoted him as captain of the team.
Pierson's mother kept him out of school three days.
Administrators did not deem him a danger, even though the coach told them he was so fearful he considered resigning. A school resource officer who is also a deputy made a report of the threat but took no further action.