A security guard at Arapahoe High School when a senior shot and killed a classmate said school officials discouraged staff from formally documenting concerns about students they saw as troubled.

Cameron Rust, who has been placed on paid administrative leave, said Friday he worries about future violence and danger at the school because administrators refuse to acknowledge problems as they are brewing.

"Arapahoe is still a very unstable environment," Rust told The Denver Post, a day after he posted a lengthy message on Facebook accusing administrators of ignoring warning signs before the Dec. 13 attack. "Something bad is going to happen, and they aren't doing anything about this."

Rust said school officials knew Karl Pierson was a threat well before he entered the school armed with a shotgun, a machete, Molotov cocktails and 125 rounds of ammunition and fatally shot Claire Davis. Claire, 17, died eight days later. Pierson also killed himself.

Click here for the complete story.