An Arapahoe High School student possibly bent on revenge against a teacher entered the Centennial school with a shotgun Friday, critically wounding a student, before using the gun to kill himself.
Arapahoe County Sheriff Grayson Robinson said that the gunman entered the school's west wing at 12:33 p.m. making no effort to conceal his weapon and immediately asked students the location of the teacher. Upon hearing the student was looking for him, the teacher left the building safely.
"It is clear that the teacher and student had a relationship," Robinson said. "The degree and level of that relationship will be determined in the days to come."
While the shooter did not get to the teacher, one student, who Robinson said was among 65-80 students in the area, was shot. She was in critical condition as of Friday night.
"Our thoughts and prayers are with her and her family," Robinson said.
Another student was taken to a local hospital for precautionary reasons and had been treated and released by late Friday afternoon.
The shooter was identified Friday night as 18-year-old Arapahoe student Karl Pierson, a resident of Highlands Ranch, who was a member of the school's speech and debate team and a national finalist in the activity. He was found dead in one of the school's classrooms within five minutes of the initial call.
Teams of law enforcement personnel continued the investigation inside the school Friday night and the sheriff said not to expect immediate answers as to the specific motive that led to the shooting. Two explosive devices were located in the school, one of which, Robinson said, had been detonated. He expects the scene to be cleared on Monday.
"We will do this investigation right," Robinson said. "We will not do it quickly."
Robinson said they believe the shooter acted alone and that his department, along with members of the FBI and neighboring agencies are conducting a thorough investigation of the suspect's home as well as a second home he had access to in the area. He added that deputies will be interviewing all friends and family he has made contact with in recent weeks and that those interviews could take up to three weeks to complete.
Robinson said it's possible the teacher was being sought by the student as "revenge" over a "disagreement."
On Friday evening, a home in Highlands Ranch on Sugarstone Circle, believed to be the residence of Pierson, was blocked off by law enforcement personnel as part of the investigation. Bomb squads were on the scene.
The shooting comes one day before the first anniversary of the mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Araphoe junior Tyler Arellano, 16, was in algebra class with 28 other students and his teacher, Mrs. Lhotta, when four shots rang out. He thought they came from an area near the west entrance.
"We were all just crying and ducking down," he said. "Nobody really knew what to do."
Arellano said the teacher told them to keep quiet, and gave them all their cell phones in case they needed to call their parents.
"She did good and stayed calm," he said.
They stayed that way for about 17 minutes, he thinks, then they heard the SWAT team yelling outside.
"They broke through the door and told us to run out as fast as we can toward King Soopers," he said. "Everyone is in shock. They don't really want to talk about it, because it was pretty scary. But I'm fine."
Parents of Arapahoe High School students were asked to go to nearby Shepherd of the Hills Church where they could reunite with their children. By Friday evening, all students and parents had been reunited, Robinson said.
As part of the investigation, cars parked in Arapahoe's west lot will not be released to their owners until Saturday afternoon or later while students' personal property left behind will not be released until Monday at the earliest, Robinson said.
Arapahoe High School will be closed on Monday, said Littleton Public Schools Superintendent Scott Murphy, while addressing the media Friday evening.
"This is a terrible day for so many," Murphy said. "It's heartbreaking.
"It is a strong community. We will stay together."
Gov. John Hickenlooper issued a statement early Friday afternoon, before heading down to the scene later in the day.
“This is an unspeakable horror and something no child, no family should have to endure," he said. "Our thoughts and prayers are with the Arapahoe High School community and those affected by this senseless act of violence. We thank law enforcement and first responders for their swift work. All of Colorado is with you.”