CENTENNIAL, Colo. (AP/CBS4) – Investigators say the student who killed a classmate before taking his own life at a suburban Denver high school described himself in a diary as “a psychopath with a superiority complex” and indicated he was exacting revenge for being teased in elementary school.

In a report released Friday by the Arapahoe County Sheriff’s Office, Karl Pierson, 18, wrote that he planned the Dec. 13 attack at Arapahoe High School to start a conversation about elementary school teasing.

“Words hurt, can mold a sociopath, and will lead someone a decade later to kill,” he wrote in a document titled “A diary of a madman.”

Police have said Pierson held a grudge against his debate coach and was targeting him when he entered the school with a shotgun, a machete, homemade bombs and 125 rounds of ammunition. Pierson shot and killed 17-year-old classmate Claire Davis before taking his own life in the school library as security officers closed in on him.

The coach escaped unharmed.

Police have said Pierson planned to harm many people. He wrote numbers and letters corresponding to the library and four other classrooms on his forearm before entering the school.

Claire Davis (credit: Davis Family)

Claire Davis (credit: Davis Family)

The shootings shocked Littleton Public Schools, one of many across Colorado that bolstered protocols for identifying the severity of threats and fashioning response plans after the 1999 shooting at nearby Columbine High School left 13 people dead. The two gunmen, both Columbine students, then killed themselves.

School disciplinary records showed that in September 2013, Arapahoe High officials deemed Pierson “not a high-level of threat” after he shouted a death threat against the debate coach after his demotion from team captain.

Pierson was allowed to return to class less than a week after the threat. Disciplinary records said Pierson showed no remorse over the incident.

The threat assessment indicated that the teen would see a psychologist once a week to talk about how to manage his anger.

Littleton Public Schools officials have refused to discuss their handling of that incident.

“The threat assessment indicated Pierson was a low level of concern,” Sheriff David Walcher said Friday. He said Pierson’s mother told the sheriff’s department that her son was not deemed a threat to himself or others after an evaluation at a behavioral health center on Sept. 9, 2013.

Two days before the shooting, Pierson was sent to the assistant principal’s office after pounding on a locked classroom door and yelling, disturbing other classrooms, according to the documents. He was sent home for the day.

Authorities have said Pierson entered the school through a door that should have been locked but was propped open.

Christina Erbacher-Kolk, a school security guard at the time, has said that administrators took no action after she and another guard saw Pierson looking up guns on his computer at school less than two months before the shooting. School officials refused to comment on Erbacher-Kolk’s statements.

Arapahoe County District Attorney George Brauchler said Pierson alone is liable.

“The criminal liability in this particular case died on the floor of the library in Arapahoe High School on Dec. 13,” he said Friday. “That is not to say there are not other questions to ask.”

Micki Jacoby, the stepmother of one of the guards, was upset the guards’ warnings were not taken seriously. “For them to dismiss their roles in all of this, shame on them,” she said.

Davis’ Parents: Help Troubled Students

Excerpts from a statement by Michael and Desiree Davis, parents of 17-year-old Claire Davis, who was shot and killed in December by a fellow student who later killed himself at suburban Denver’s Arapahoe High School. An investigative report into the shootings by Karl Pierson was released Friday.

“This crime report shows that Karl Pierson was an adolescent that allowed himself to become filled with confusion and darkness, and he failed to see any love around him or any hope for the future. The result was a terrible tragedy for all of us – not only our family, but for all the kids and staff at Arapahoe High School, our entire community, the State of Colorado, and all of the people across the country and around the world that have sent us their condolences and have held us up in their thoughts and prayers.

“As we all consider this report in greater detail, our family wishes to ask school officials and other stakeholders – particularly our State legislators – to thoughtfully and expeditiously explore how to create positive and safe school climates that are better prepared to prevent and change inappropriate behaviors, as well as better address the emotional and psychological needs of adolescents in our schools. The people of Colorado deserve more than to have to sit idly waiting for the next student in imminent crisis to harm or kill another person or themselves.”


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