ARAPAHOE COUNTY, Colo. -- New details were released about the Arapahoe High School shooting at a press briefing hosted by the Arapahoe County Sheriff and District Attorney on Monday, the most telling of which laid out a specific timeline of the attack.
In total, Arapahoe County Sheriff Grayson Robinson said, the shooting took less than 1 minute and 20 seconds. While brief, the attack, which occurred on Dec. 13, left two students dead – senior Claire Davis and the shooter Karl Pierson.
Robinson continued to say that based on the available evidence as of Monday, is still believed that Pierson acted alone and was looking for revenge after getting demoted on the school’s debate team.
"There is no question that this was very deliberate and planned event," Robinson said.
One piece of disturbing news was that the attack began when Pierson entered the school through an open door that should have been shut and locked, Robinson said.
Robinson called Pierson an "evil individual," and said he went bowling the night before the attack by himself and made purchases related to the attack the morning before it occurred.
"He (Pierson) conducted his business as he normally would," Robinson said. "He gave no indication anything was amiss."
District Attorney George Brauchler described the shooting as an incident is one that "hits close to home for me," saying Arapahoe High School is very close to his home. Brauchler confirmed that the firearm Pierson used in the attack, a 12-gauge shotgun, had been obtained legally, but offered few other details about his office's investigation.
"We are not at a place to be unsealing affidavits for search warrants," Brauchler said.
In addition to the shotgun, it was also revealed that Pierson had 125 rounds of ammunition, a machete and three Molotov cocktails. Robinson said that Pierson fired six rounds inside the school and threw one of the homemade explosives at a shelf inside the school's library, starting a fire.
One of the six rounds was directed at Davis, Robinson said, who died of her wounds on Dec. 21.