KUSA - An Arapahoe High School security guard says the school and the Littleton School District didn't do enough to prevent the Dec. 13 shooting.
Arapahoe High School student Claire Davis was shot and died eight days later. Investigators say the shooter was Karl Pierson, another student at the school, who took his own life after shooting Claire.
In a lengthy Facebook post, Cameron Rust outlines what he says happened before and after the shooting.
"People don't just make choices all the sudden, things lead up to it," Rust said. "Looking up guns, making a threat, behavior patterns changing, those are red flags."
In his post, Rust says the high school's administration is responsible for a "lack of action."
In a Friday interview with 9NEWS, Rust said Pierson could have been stopped and helped before the situation escalated.
Rust said before the shooting, Pierson threatened a teacher, for which he was disciplined. He was the same debate coach he went after on Dec. 13. Rust said he and other members of his team saw Pierson research guns while at school.
"We noticed one afternoon in the lunch room Karl was looking up guns on his computer, and after we noticed that, he quickly closed his computer," Rust said. "We immediately told our supervisor what we saw. We were told he would bring it up in our administration meeting. That following Monday after the administration meeting, we were told there is nothing they can do about that. It was his personal computer, and he could look up what he wanted."
The day before the shooting, Rust said Pierson was sent home after an angry outburst. Rust says the school knew Pierson had issues.
"They've said it multiple times on multiple occasions," Rust said. "'We will see Karl Pierson on the news someday, it just will not be at Arapahoe High School."
Rust told 9NEWS his school safety concerns were ignored and dismissed the school didn't act.
Rust said he's coming forward to force the administration to "own up to their mistakes and make necessary changes going forward."
Rust said he's been placed on paid administrative leave.
The Arapahoe County Sheriff's is investigating the shooting.
In an e-mail, Sheriff Grayson Robinson told 9NEWS:
"From the initial stages of the on-going investigation, Mr. Rust was the subject of interviews conducted by the Arapahoe County Sheriff's Office. Our investigators plan to re- interview him in the future, as well as numerous other individuals, as part of the on-going investigation into the tragedies associated with the December 13, 2013 incident. The critical responsibility of determining the truth, established by facts and evidence, is our key focus and absolute responsibility to the community and to the Davis family. That responsibility will be accomplished in a complete and thorough manner.
There will be no further comment regarding this matter, as this point in time, as we will not be distracted from our critical responsibilities of the on-going investigation, nor will we tolerate any effort to divert our attention or obstruct our investigative responsibilities."
9NEWS contacted the school district Thursday and Friday for comment, but haven't heard back.
The district sent out an email to parents Friday afternoon. It says in part, "Much of the conversation, however, is based on inaccurate information, rumor, and innuendo. I would encourage all Warriors to wait for the sheriff's investigation to come to a close before drawing conclusions."
READ THE FULL LETTER TO PARENTS HERE
(KUSA-TV © 2014 Multimedia Holdings Corporation with The Associated Press)