Arapahoe High School administrators repeatedly ignored signs an 18-year old student was a threat before he killed a classmate and himself in 2013, a report said.
The school and the school district could have intervened on Karl Pierson long before he stormed the school in 2013 with a shotgun, a machete and homemade bombs, the University of Colorado's Center for the Study and Prevention of Violence and the University of Northern Colorado's Department of Criminal Justice found in the report released Monday.
Pierson killed Claire Davis, 17, and then himself on Dec. 13, 2013.
The center found administrators failed to share vital information, perform critical threat assessments and made continual poor decisions -- 27 in total -- about Pierson that allowed the shooting to unfold. Records dating back to his elementary school days show a pattern of violence, an early indicator for continuing problems.
"[Arapahoe High School's] and [Littleton Public School's] system failed at many points to get a handle on [Pierson's] problems, in spite of the fact that there were many warning signs and many opportunities," the report found.
"Not one [Arapahoe High School] teacher, administrator or staff person had a complete record of [Pierson's] history of concerning behaviors over his more than three years at [the high school], making it challenging to adequately assess the threat he presented," the report found.
The report came as part of an agreement between the school district and Davis' family not to sue.
"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," Michael and Desiree Davis, Claire's parents, said in the report introduction. "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."
The report made several recommendations for changes, including greater sharing of information and better access to mental health assistance.
"The institutional barriers within schools, districts and our culture will need to be dismantled, including the belief that schools are powerless to manage mental health issues," the report said. "Schools can manage mental health and social support issues. The task is complicated but it is not impossible. The promotion of school safety will require the implementation of multiple mitigations in parallel."