Teen gunman at Arapahoe High School bought ammo on day of attack

Karl Pierson, 18, was old enough to buy a shotgun under Colorado law – and he bought it a week before he stormed into Arapahoe High on Friday in search of the school debate coach. He bought ammunition that morning, officials say.

The Colorado high school student who shot and seriously injured one of his classmates came to school laden with a extensive array of weapons and an apparent intent to do harm.

Karl Pierson, a senior at Arapahoe High School, walked into school a little after noon on Friday, wearing a bandolier of ammunition and a backpack that carried three molotov cocktails. The 18-year-old was also armed with a machete and a pump-action shotgun, according to The Denver Post.

In a matter of 80 seconds, Mr. Pierson had entered the school, fired five rounds, and shot a fellow student he apparently did not know, Claire Davis, at point-blank range in a hallway near the library. Pierson then set fire to a part of the library using a molotov cocktail, before taking his own life as an on-site sheriff's deputy arrived. 

Claire's family reports that she is in a coma, according to the DenverChannel.com.

Colorado law allows 18-year-olds to buy shotguns but not handguns. Pierson bought his gun on Dec. 6 at a local store, and then purchased a large amount of ammunition the day of the shooting, the Post reports.

A team of investigators that includes the local sheriff’s office, the Colorado Bureau of Investigation, and the Federal Bureau of Investigation has finished scrubbing the school for details to try to discern what exactly happened on Friday, and school district administrators will be allowed back into the building this week, the Associated Press reported.

The sheriff’s department will also allow students to go back into the building to collect their belongings, in two-hour shifts. 

Officials canceled classes at Arapahoe High School until the new year, after winter break, according to the AP.

Investigators have not offered an official explanation about what motivated Pierson to come to school laden with weapons. The Denver Post reported that one of Pierson’s friends believes Pierson might have set out after the school’s debate coach.

Joe Redmond told the Post that his classmate had threatened to kill the school’s debate coach after a conflict over Pierson’s position on the debate team. But after the two students talked things over last week, Joe said, Pierson seemed to be fine.

Twenty-four hours before Pierson's attack, he was joking and talking politics, Joe said.

"We were back to our old conversations," he said. "I have no idea what happened [over the next 24 hours]. I can only speculate." 

The shooting at Arapahoe High School occurred a day before the one-year anniversary of the Newton, Conn., school shooting, which left 28 dead, including 20 children. Investigators say there is no connection between the two events, the AP reports.

Colorado lawmakers enacted stricter gun control laws this year after the recent mass shootings in Aurora, Colo., and Newton. However, some sheriffs in the state are balking at enforcing the new controls, especially on ammunition, The New York Times reported Monday. 

In September, Colorado voters recalled two elected officials for voting for tighter gun control restrictions.

Arapahoe High School is in the Denver suburb of Centennial, eight miles from Columbine High School in Littleton, where in April 1999 two students gunned down 13 people before killing themselves. Centennial is 20 miles from Aurora, where a gunman killed 12 people after opening fire in a movie theater in July 2012.