DENVER (AP/CBS4) – Administrators at a high school in Littleton dismissed increasingly obvious warning signs that a troubled student was a threat before he killed a classmate and himself two years ago, a report released Monday shows.

Arapahoe High School staff poorly gauged the rising threat Karl Pierson, 18, posed months before he stormed the school with a shotgun, a machete and homemade bombs and shot Claire Davis, 17, in December 2013, according to the 141-page report by the University of Colorado’s Center for the Study and Prevention of Violence.

Claire Davis (credit: Davis Family)

Claire Davis (credit: Davis Family)

The shooting might have been prevented if school staff had kept detailed and more widely accessible records documenting concerns over Pierson, the report says. Administrators also failed to thoroughly investigate threats he made.

“Unfortunately there are many instances that this student demonstrated,” Sarah Goodrum, some concerning behaviors that were not addressed appropriately,” one of the report’s authors, told CBS4.

Davis’ parents sought the study as part of an agreement that they would not sue the school district in exchange for information about the shooting. Michael and Desiree Davis have long believed the school missed Pierson’s repeated red flags, and successfully pushed for legislation to allow lawsuits against Colorado schools when there are shootings or other violence.

“The angry young man that murdered our daughter was a student in crisis who desperately needed guidance in a different direction from the one he pursued,” the Davises wrote in a message included in the report. “The lesson to learn is not that our schools should be less tolerant and more punitive, rather that our schools are now, as never before, in a unique position to identify and secure help for troubled students.”

Authorities have said Pierson held a grudge against his debate coach and was targeting him. He first shot Davis, who was was with a friend in a hallway, before taking his own life in the school library as security officers closed in on him. The coach, Tracy Murphy, escaped unharmed.

Brian Ewert, who became Littleton Public Schools superintendent last year, said he agreed with the study’s findings, and administrators will “learn from the missed opportunities we had to disrupt Karl Pierson’s path to violence.”

Karl Pierson (credit: CBS)

Karl Pierson (credit: CBS)

“There were warning signs, each in isolation and to some degree disconnected,” Ewert wrote in an email to The Associated Press. “The challenge was connecting the many isolated incidents into a significant threat; the district and the school failed to connect the dots.” No single teacher or administrator had a complete record of Pierson’s problems throughout high school.

School officials deemed Pierson not a danger after a staffer overheard him in a school parking lot threatening to kill Murphy on Sept. 3, which left Murphy so fearful he considered resigning. Pierson was not suspended and was allowed to return to class less than a week later.

The assistant principal who assessed Pierson was never trained in the district’s threat-assessment protocol, nor was the principal and most of the staff, the study concluded. Administrators then failed to meaningfully follow-up with Pierson or create a support and safety plan that might have thwarted his violence, the report says.

“What we found also was that there was kind of a climate of ‘We’re kind of a perfect school, so nothing bad could happen here,'” William Woodward, another co-author of the report, told CBS4’s Kelly Werthmann. “Therefore, when people raised issues, they were kind of dismissed as not being very important.”

The report points to more than a dozen other failures by school officials, including the decision not to take action after Pierson had a startling outburst in his Spanish class just two days before the shooting. After a student locked him out, he pounded on a locked classroom door so hard that teachers in other classrooms could hear him.

Officials never searched Pierson’s backpack, locker, journals or computer, which later revealed his extensive planning.

“What we really found is that there wasn’t one thing that could’ve interrupted the student’s plan,” Goodrum said. “What we think is really important to learn from this particular case is that there wasn’t one catastrophic failure. Instead there were a lot of small mistakes that were made in Arapahoe High School management of the student, his discipline issues and in how he was supported in the weeks and months following his initial threat.”

The school district has already made some changes, Ewert said. Among dozens of recommendations, the study says the district should promote an environment where staff feel free to report concerns and mistakes without fear of punishment.

Ewart released a report to the school board Monday acknowledging that some warning signs were missed.

“We are profoundly sorry that this may have contributed to the loss of two students’ lives that day,” he said.

After the shooting security guard Christina Kolk told CBS4’s Rick Sallinger she gave warnings about Pierson that went unheeded.

“Do you believe if the school district had listened to you Claire Davis might be alive today?” Sallinger asked Kolk at the time.

“I believe she might be, yes, because I think there would have been more staff involved to help Karl,” Kolk replied.

Her attorney Dan Recht says Kolk now feels vindicated,

Ms. Kolk is very hopeful this investigation will lead to reform in school district and applauds parents for this very creative way of resolving the case.

LINKS: Read The Full Report | Report Presented To The Denver Foundation

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