DENVER -- An Arapahoe High School security guard is speaking out. He says there were warning signs that could've prevented last month's shooting that killed senior Claire Davis.
Cameron Rust says those warning signs were ignored. He spoke with Channel 2's Julie Hayden a day after he wrote a post on Facebook detailing some of his concerns.
He says Pierson had made a specific threat to kill one of the teachers at Arapahoe. Even after that ongoing problems continued with the student according to Rust. That included an altercation the day before the shooting.
Rust says that when he raised general concerns about school safety, he was "dragged" into the principal's office and told don't ever put anything in writing again.
He is one of two security guards who confronted the gunman, Karl Pierson on December 13th.
"Karl was probably 10 to 15 feet away just kind of pointing the gun at us and kind of giving you the look of 'come on in, see what happens," Rust says about encountering the student after the shooting.
While first responders in general were called heroes for their handling of the shooting, the "first" first responder, Rust, says the school has isolated him from the beginning and to this day won't let him back into the school or at work.
He says he doesn't know why. He does say he's on paid administrative leave.
He points out that he was raising concerns weeks before the shooting about the way the school was handling Pierson and the death threat he made against the teacher.
"That he threatened to kill Tracy Murphy ... we were also told that Karl's mother decided to pull him out of school for three days and had reassured us that he was just angry when he said it and that nothing would happen. And then we were just told to keep an eye out for things," Rust says.
Authorities have said Murphy was the shooter's target, but the teacher was warned and was able to get out of the building.
A few weeks later he saw Pierson looking at a gun purchasing website on his computer at school. Rust reported what he saw.
"We then got told that it was his personal computer and that he could look up whatever he wanted and there was nothing that we could do," he says.
Rust says the school had made it clear in general: Don't write anything down. "We were told to just don't put things in writing and if you have an issue bring it to your supervisor and they will handle it from there. And then the ultimate decision is above us," Rust says.
Like other first responders, Rust risked his life for the students that day and he still worries about them today.
"They're kids. They're the eight wonders of the world, you know. So, they needed help. They still need help," he says.
Investigators say they plan to re-interview Cameron Rust. Other than that, neither law enforcement nor the school district are commenting about what he says.