When a student armed with a shotgun entered Arapahoe High School Friday, the frenzy of violence lasted minutes but will take investigators days to fully unravel. However, the county sheriff is already praising the reactions of his deputies.

Arapahoe County Sheriff Grayson Robinson said the first deputy on the scene was a school resource officer who announced the situation over his radio at 12:33 p.m.. Immediately afterward, the deputy followed the “active shooter protocol” and went immediately to find and eliminate the threat.

“The officer went immediately to the threat, as he was trained,” Robinson explained.

The shooter was later identified as Karl Halverson Pierson, an 18-year-old senior who was upset about being kicked off the speech and debate team by the librarian who coached the team.

As Pierson walked the halls and entered the library, witnesses say he asked for the faculty member by name.

Senior Max Minne told CALL7 Investigator Keli Rabon, “the shooter just ripped through the door, started yelling ‘Where’s Murphy?'”

The students fled the library through another door and Minne said they exited through a smoke filled hallway.

Meanwhile, Robinson said, deputies were tracking the suspect.

“Within 5 minutes, [deputies] found the suspect dead inside the school,” Robinson said. “Appears to us that the shooter is dead as the result of a self-inflicted gunshot wound, but that is under investigation.”

“I believe the shooter took his life because he knew he had been found,” Robinson also said.

Only one other student was shot, a 15-year-old girl who is in critical condition after undergoing surgery Friday at Littleton Adventist Hospital. Her identity is not yet known.

More than 2,100 students attend Arapahoe High School where nine out of 10 graduates go on to college, according to the Littleton Public Schools website. All of the students were locked down inside the building for about 90 minutes before a slow, orderly evacuation began.

“Sometimes we would hear yelling or dogs barking,” student Afton Phelps said. “We knew it was the SWAT team but it was still scary.”

Each of the students had to hold their hands in the air and be searched before they left the school grounds.

“They were evacuated very slowly, deliberately and meticulously,” Robinson said.

The sheriff explained his deputies had to make sure there were no other students or individuals that were collaborating with the suspect.

In his media briefings following the shooting, Robinson repeatedly praised the response of his deputies and the effectiveness of the protocol they followed. He also said he felt no additional security would have been more effective in preventing the tragedy.

Source: ABC News