Discipline against student thought to have sparked Colorado shooting

The teenage gunman who badly wounded a fellow student and then shot himself to death at a suburban Denver high school apparently acted in retaliation for discipline he received months ago from the school's debate club coach, the county sheriff said Saturday.

The shotgun and ammunition used by the suspect, Karl Pierson, in Friday's shooting were legally purchased from local retailers, Arapahoe County Sheriff Grayson Robinson said.

Pierson, a senior remembered by classmates as studious yet argumentative – and described by some as socially awkward – was 18 years old when he made the purchases, the minimum age for buying a shotgun or rifle in Colorado.

The sheriff's statements at a news conference shed new light on the circumstances of a shooting that unfolded in less than a minute and a half, and was the latest of more than two dozen shootings to shake U.S. school campuses this year.

Pierson fired six shots from a pump-action shotgun between the moment he walked into Arapahoe High School on Friday and the moment he killed himself in a library as a school security officer closed in on him, Robinson said. Authorities believe he intended to shoot multiple people.

The attack lasted just 80 seconds but reopened scars in a community traumatized by mass shootings at Columbine High School in 1999, an Aurora movie complex in 2012 and in Newtown, Conn., a year ago Saturday.

Arapahoe senior Claire Davis, 17, who was sitting with a friend when Pierson entered the library, was shot in the head.

Students and residents held a candlelight vigil for Davis Saturday night at a park near the school. Davis remains hospitalized in critical condition, according to the sheriff.  

Pierson's original target was believed to be a librarian who coached the school's speech and debate team. Pierson was on the team, and was disciplined in September by the librarian for reasons Robinson said were under investigation. Pierson made some sort of threat in September against the librarian, whose name was not released.

Students and a teacher said Pierson was an Eagle Scout who finished at the top of speech competitions. He competed in extemporaneous speaking — in which students prepare short speeches on current events — in the National Forensic League's national tournament in June in Birmingham, Ala.

"I think he (Pierson) really cultivated his speech and argument skills and really thought that was a big part of his identity," said Steve Miles, an English teacher who taught Pierson as a freshman. "He probably thought it was a pretty crushing blow to get kicked off the debate team."

The faculty member believed by investigators to have been Pierson's intended target managed to flee the school unharmed. But the 17-year-old classmate gunned down at point-blank range, apparently at random.

Robinson also said Pierson entered the school carrying a machete, an ammunition belt and three Molotov cocktails, one of which he ignited in the school library moments before shooting himself in a corner of the room with his own shotgun.

His body was found by law enforcement officers, who were closing in on the youth but never fired a shot.

So far this year, there have been 28 shootings on U.S. school grounds during school hours, including Friday's incident at Arapahoe High, according to a tally kept by the gun control advocacy groups Mayors Against Illegal Guns and Moms Demand Action for Gun Sense.

Centennial is also where James Holmes, the former graduate student charged with shooting 12 moviegoers to death in nearby Aurora, Colo., in July 2012, is being held in custody, awaiting trial on capital murder charges.

Al Jazeera and wire services