LITTLETON, Colo. - Investigators who looked into the deadly shooting at Arapahoe High School say "many small errors" were made and there were "many missed opportunities" to intervene with the gunman

prior to the shooting.

The report released Monday was done by The University of Colorado Center for the Study and Prevention of Violence and commissioned by The Denver Foundation.

Senior Karl Pierson shot and killed fellow student Claire Davis on Dec. 13, 2013, and then killed himself.

The findings revealed three major failures within AHS and Littleton Public Schools in the months and years leading up to the shooting:

  1. a failure of information sharing,
  2. a failure of threat assessment, and
  3. a failure of systems thinking.

According to the report, there were "many missed opportunities" to share information about the gunman's "concerning behaviors" and to intervene with the gunman before the shooting.

"...[T]he Sheriff’s Report clearly states that at least ten AHS students had substantive concerns about [the gunman's] anger problems and gun ownership prior to the shooting, but only one student reported their concern to a counselor and no students reported their concerns to Safe2Tell," the report states.

"If just one student or teacher, had called Safe2Tell, this tragedy might have been averted," said the report, referring to a tip line for reporting possible threats.

Authorities believe the gunman was targeting his debate coach when he entered the school with a shotgun, machete, homemade bombs and 125 rounds of ammunition. Investigators said he shot and killed Davis, 17, before turning the gun on himself in the school library as security officers closed in. The coach escaped unharmed.

Two school security guards told investigators they saw the gunman looking at pictures of guns and mass shootings on his computer six weeks before the shooting. Also, police found a book about the Columbine High School attack when they searched his mother's home.

Arapahoe County Sheriff Dave Walcher said school officials did not suspend the gunman in September and allowed him to return to class after he threatened to kill the debate coach, who had recently demoted him as captain of the team.

The report listed a series incidents involving the gunman (referred to as "KP") that could have been addressed differently:

  • Decision to not build a safety and support action plan for KP after incidents of violence in elementary school, when early violence is clearly a strong risk factor for later violence
  • Decision to ignore the possible impact of his parent’s divorce
  • Decision to not enlist the help of one adult at AHS that KP trusted in his safety and support action plan
  • Decision to not have a safety and support action plan (e.g., mental health referrals, follow-up meetings) when KP yelled “f***” in class and was suspended
  • Decision to not follow-up on KP’s use of inappropriate “penis” line in debate competition
  • Decision to not follow up on KP’s claims of being bullied by others and being a bully to others
  • Decision to not empirically validate LPS’s threat and risk assessment tool
  • Decision to not treat KP’s violation of the Assistant Principal’s request that he not attend speech and debate team practices as evidence of “boundary probing”
  • Decision to only use two threat assessment team members in the threat assessment process, despite state and federal guidelines
  • Decision to leave the School Resource Officer out of the threat assessment process
  • Decision to not assign a staff member to serve as the “information vortex” for KP during the threat assessment
  • Decision to not have a district-level Safe2Tell training policy for high schools
  • Decision to not forward KP’s threat assessment to the district for review
  • Decision to not thoroughly check the facts and collect collateral information on KP in the threat assessment process
  • Decision to not tell a student’s teachers the reason for a threat assessment, detention, or suspension
  • Decision to train threat assessment using only didactic and audio visual resources
  • Decision to not formally suspend KP for his threat to “kill” Mr. Murphy (the debate coach)
  • Decision to not formally suspend KP for his outburst in Ms. Lombardi’s Spanish class
  • Decision to not obtain video surveillance footage of KP making a threat about Mr. Murphy in parking lot
  • Decision to allow KP to return to school without the threat assessment team obtaining release of records from KP’s private therapist
  • Decision to allow KP to stay in school, when requested release of mental health records was not provided, as requested
  • Decision to only have one follow-up meeting to discuss KP’s progress with the safety and support action plan
  • Decision to not recommend a Student Intervention Team (SIT) to support KP when his grades began to decline
  • Decision to not inform the threat assessment team about KP’s viewing of guns and mass shootings on his laptop
  • Decision to not search KP’s computer, locker, or possessions for confirmation of his viewing of guns and mass shootings
  • Decision to not report KP’s purchase of a gun or interests in guns, as well as his anger problems, to Safe2Tell
  • Decision to not re-open KP’s threat assessment case after being told he had an angry outburst in class and had a gun

The report states that improvements have been made but more needs to be done to ensure student safety.

Read the full report here:

"...[P]reliminary evidence indicates that AHS staff and LPS administrators have made several changes in their approach to school safety since 2013, and those changes represent important steps in the right direction... However, a great deal of progress still needs to be made."