One minute and 20 seconds.
That's how long Arapahoe County Sheriff Grayson Robinson said Karl Pierson's rampage lasted. Pierson, 18, entered Arapahoe High School brandishing a shotgun Dec. 13, seriously wounding Claire Esther Davis, before killing himself, the sheriff said.
After viewing security-camera footage of the scene, Robinson offered some new and some revised information Dec. 14, including the name of the single gunshot victim. Davis is a 17-year-old senior at Arapahoe High in Centennial, a horse enthusiast and, says Robinson, a completely innocent victim who had no time to run from her attacker before he shot her point blank in the head.
"She is a young woman of principle, she is a young woman of purpose, she is an innocent young lady, and she is an innocent victim of an evil act of violence," the sheriff told a large contingent of media outside the school.
A statement released by Davis' family says she has severe head trauma and is still in critical condition. They requested privacy for themselves and Littleton Adventist Hospital, and thanked the trauma team there for saving their daughter's life.
"She needs your continued prayers," read the statement. "We would like to thank our family, our friends, the community and the equine community for their outpouring of love and support."
Davis was the lone gunshot victim, the sheriff confirmed Dec. 14. A student near her at the time of the shooting was taken to a hospital as a precautionary measure.
According to Davis' Facebook page, she's a member of the Colorado Hunter Jumper Association and attended Vellshire Riding School.
Robinson said the security footage shows Pierson, an Arapahoe student, parking on the north side of the building at 12:33 p.m. and getting out of his vehicle with the pump-action shotgun in plain view. He had a bandolier full of ammunition slung across his chest and was carrying a machete. He also was wearing a backpack that turned out to contain three Molotov cocktails.
Contrary to his earlier view that Pierson was only after his debate coach, Tracy Murphy, Robinson now believes Pierson was intent on killing or injuring as many people as he could, though the faculty member was the primary target. He still believes the incident was likely a reaction to some sort of dispute between Murphy and Pierson, who reportedly made threats against the educator in September because he disagreed with a disciplinary action.
Murphy was quickly alerted to Pierson's presence Dec. 13 and was able to safely leave the grounds before the student could find him.
Pierson purchased the firearm on Dec. 6 at a local retail outlet, which was legal because he was 18, said Robinson. He had purchased at least some of the ammunition in the morning before the shooting.
Pierson entered the school through a door adjacent to the school library on the north side of the building and immediately shot a random round down a hallway. He then walked up to Davis and shot her point blank.
"There was no time for the victim to get away from the shooter," said Robinson.
Pierson then took another random shot, went directly to the library and set off one of the bombs, which set at least three bookshelves on fire. He shot a fifth round, but by now he could hear the school resource officer — an Arapahoe County sheriff's deputy — heading at him full speed.
Robinson said the resource officer, along with an unarmed security guard and two administrators, heard the first shot and immediately began running from the cafeteria to the library. The resource officer was screaming at kids to get down and identifying himself as a deputy sheriff.
As soon as Pierson heard the commotion coming toward him, he walked to a corner and shot himself, said Robinson.
"It's typical for a shooter to shoot until confronted by a person in authority," he said. "The response from officers was absolutely critical to the fact that we did not have additional injury and/or death."
Robinson said the building will likely remain a crime scene until at least mid-afternoon on Dec. 15. Scott Murphy, Littleton Public Schools superintendent, said it is unlikely regular classes will resume until after next week. Counseling continues to be available for anyone in the community with a need to talk about what happened.
"This has truly been a village and a family pulling together in a difficult time," said the superintendent.
As part of the investigation, authorities searched three properties around the metro area, including Pierson's home in Highlands Ranch. Robinson would not divulge what was found, but reiterated that he believes Pierson acted alone.
"We found nothing that would lead us to believe there were coconspirators," he said.
Robinson added that even after Arapahoe High — the largest of LPS' schools with more than 2,000 students — is turned over to the school district, the investigation won't be over.
"We still have a great deal of work to do," he said.