CENTENNIAL, Colo. - A student gunman who shot two students inside Arapahoe High School -- critically injuring a 15-year-old girl -- was targeting the school faculty member who had just kicked him off the school's debate team, CALL7 Investigators have confirmed.
The faculty member -- the school's librarian, Tracy Murphy -- escaped without injury.
The gunman -- whom CALL7 Investigators have identified as senior Karl Pierson -- died from an apparent self-inflicted gunshot wound and was found in a classroom by a deputy who had called for additional help to "active shooter" situation just 5 minutes earlier.
7NEWS has learned that Pierson -- who was described as exceptionally bright -- was upset about being booted from the debate team.
"This shooting was the result of revenge on the part of the shooter because of a confrontation or a disagreement between the shooter and the teacher that the shooter was looking for when he entered the school just before 12:33," Arapahoe County Sheriff Grayson Robinson said.
Detectives are executing a search warrant at the gunman's Highlands Ranch home, looking for additional evidence," Robinson's said.
Officers are also searching the car he left on the school's parking lot and another home he had "temporary access" to, Robinson said.
Of the two students who were shot, one is in critical condition at Littleton Hospital, where she underwent surgery earlier Friday. She has not been identified.
The other student who was shot has minor injuries and was treated and released from Swedish Hospital.
Three students suffered anxiety attacks during the school evacuation, Grayson said. Two of those students were released to their parents and the third student was taken to Swedish where the student was treated and released.
Two Molotov cocktails were found inside the school, Robinson said. One was detonated inside the school and may have caused the significant amount of smoke deputies were faced with when they first responded to the scene.
The second device was found inside the school during the search after the shooting. That device was rendered safe and was never deployed, Robinson said.
-- Janitor: Student wearing tactical gear ran through school --
The shooter was armed with a shotgun and was looking for a specific teacher that he identified by name when he ran into the school, Robinson said.
The shooter walked into the west side of the school at 12:33 p.m. on Friday.
Custodian Fabian Llerenas told 7NEWS that he saw a student dressed in military or tactical gear running through the school. He thought the black object swinging on the gunman's arm was a guitar case.
"It just looked weird," Llerenas said. "He went in and that's when I heard two pops. That's when I knew. I said, 'They are shooting in the school.'"
Llerenas said he called for help and took the threatened staff member with him to his truck.
"He knew he was the target," Robinson said as he praised the teacher for leaving in hopes that it would help remove the threat from the school.
"When the teacher found out, he exited," Robinson said.
Seconds later, Robinson said, a student was shot.
Initially, Robinson said that student had confronted the gunman, but later Robinson said that student may have simply been in the area and was shot.
Arapahoe High School student Courtney Leytoldt told 7NEWS she heard a girl running down the stairs yelling, "Help me, help me, there's a shooter." She said that girl was covered in blood.
Leytoldt said she was in yoga class and that her teacher put all the students in a closet to protect them.
Robinson said as soon as the first deputy was notified of the situation, he followed the "active shooter protocol" and called for backup before seeking out the gunman.
"The officer went immediately to the threat, as he was trained," Robinson explained. "Try to go to the threat and eliminate the threat."
"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."
Robinson said authorities know the gunman's identity, but are not yet releasing it. Authorities are interviewing people who known the gunman or have some sort of association with him.
Thousand of students were evacuated safely but 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 explained.
He said deputies wanted to make sure there were no other students or individuals that were collaborating with the suspect.
Robinson said that the gunman acted alone.
-- Parents reunite with kids, districts react to lockdown --
Hearing of the lockdown and shooting by students inside the school, panicked parents fled to the high school and were told to go to Shepherd of the Hills Church and Euclid Middle School, where they would be reunited with their children after they are cleared by officers.
Robinson said there is no indication that there is a tie between the shooting at Arapahoe High School and the one year anniversary of the deadly school shooting at Sandy Hook Elementary School on Saturday.
Arapahoe High School is at 2201 East Dry Creek Road in Centennial. It is part of Littleton Public Schools, which locked down all schools Friday afternoon when there were initial reports of a shooting.
Several other school districts went on alert, declaring lockdown or secured perimeter including Elizabeth schools, Cherry Creek Schools, Douglas County Schools and Aurora Public Schools.
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.