5 of Colorado largest school districts investigate more than 400 threats this school year

DENVER - Five of the state's largest school districts have investigated more than 400 threats by students this school year and put 40 of them at the highest levels of concern, according to records obtained by The Denver Post.

But more than a month after the fatal shootings at Arapahoe High School, administrators at Littleton Public Schools still won't say if a threat made by gunman Karl Pierson in September prompted the district's highest security response.

Pierson, a senior at Arapahoe, entered the school through a door that was propped open on Dec. 13 armed with a shotgun, a machete, three Molotov cocktails and more than 125 rounds of ammunition. He killed student Claire Davis and took his own life in the school's library.

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