CENTENNIAL, Colo.—An 18-year-old high school student reportedly frustrated when he was ejected from the school debate club has been identified as the shooter who opened fire at a suburban Colorado high school Friday, wounding another student before killing himself.
Karl Halverson Pierson, 18, was said to be angry at the school debate coach and entered the school shortly after noon Friday with a shotgun, repeatedly calling the teacher's name, according to interviews with students and law enforcement officials.
When he found the teacher, he "shot once and missed" before the teacher fled, according to senior Frank Woronoff, 18, who talked with the instructor—who seemed shell-shocked afterward—outside the school as students fled for safety.
"He could barely speak. All he could say were the same statements over and over. He seemed like he might have a panic attack," Woronoff said of the teacher, whose name has not been released by authorities.
Contrary to earlier reports, there was only one gunshot victim, a 15-year-old girl, Arapahoe County Sheriff Grayson Robinson told reporters. "There's no reason to believe she was a target," the sheriff said, adding that it was unclear whether the girl had tried to confront the shooter.
A second girl was mistakenly thought to have been shot, but she had blood on her only because she had come into contact with the injured girl, Robinson said.
The wounded student remained in critical condition in a local hospital. The rest of the high school was evacuated earlier Friday, with students filing out with arms raised—a chilling image reminiscent of other school shootings.
The shooting in Centennial, a city of about 100,000 not far from Denver, reminded many of the deadly 1999 attack at nearby Columbine High School in which two students killed a dozen classmates and a teacher.
This latest shooting also comes as the nation prepares to commemorate the first anniversary Saturday of the massacre at Sandy Hook Elementary School in Newtown, Conn., where 20 children and six educators were killed by a lone gunman before he committed suicide.
Investigators said they recovered two Molotov cocktails after Friday's shooting, one of which had detonated, but said it was not yet known who owned the shotgun used in the assault or when it was purchased.
Authorities will execute search warrants on three locations — the home where Pierson lived with his mother, his father's home in Denver and Pierson's car, which is still in the school's west parking lot, police said.
Robinson said authorities hoped information gleaned from the searches "will help us put the pieces together."
Friends described Pierson as an intelligent, likeable youth who liked to talk about politics and was a strong advocate of gun rights, though they said they had never seen him with a gun.
"I had class with him and knew he was very outspoken and willing to contribute, and also that he had a controlled temper he would use during discussion," Carl Schmidt, a fellow senior, told The Times in a Facebook message.
Pierson had friends, a younger sister and a middle-class family. He was "slightly geeky," Woronoff said, but not a loner. He attended school dances and competed at track meets. "He was one of the nicest, most down-to-earth kids I knew."
But he was picked on.
"The kids at school knew how to push his buttons," Woronoff said. "He was bullied a bit, but he didn't stop. He'd get right back up."
Though Pierson had "a multitude of friends," Schmidt said, "only those that could cope with his personality became close with him."
Pierson appeared to care passionately about debate, and became upset over a disagreement with the debate coach, friends said.
Joe Redmond, also a fellow senior and one of three co-captains of the debate team, said Pierson was kicked off the team and suspended from school in September for a few weeks after threatening the coach.
"When he came back he was really, really angry," Redmond said.
The debate team won first place in a tournament Saturday, Redmond said, and when students returned to school Monday, Redmond asked Pierson if he would consider rejoining the team.
Pierson told Redmond that he still hated the teacher, and said, "Apparently you get suspended for threatening to kill a teacher." He said Pierson went cold at that point, looked at Redmond, and then looked at the ground.
Redmond said that Pierson and the teacher had argued over changes Pierson had wanted to make to the debate team.
"He doesn't take a no very lightly," Redmond said.
Redmond said his team's victory on Saturday may have made Pierson upset that he was no longer on the team. He said Pierson was the best debater on the team.
Redmond said Pierson also seemed to be affected by the divorce of his parents within the last two years.
"At the end of the day Karl was a good person, and I hate the idea that he might be defined by his ending acts," Redmond said. "I loved to be around him. I loved to talk to him. It's always a shame when you hear friends making bad choices, but this one was particularly devastating."
Pierson was active on social media, filing his most recent public Facebook update on Dec. 5, when he changed his cover photo to a melded image of the recently deceased actor Paul Walker, the late former South African leader Nelson Mandela, and Brian the dog from the television show "Family Guy," all sitting in a car.
On the Arapahoe Speech and Debate club's Facebook page, Pierson was a frequent poster, motivating his teammates with funny images and countdowns to future debates.
"39 more days till nationals!" he posted on May 7, with a link to a meme of Joe Biden with "#Turn myswagon" as the caption.
On June 18 he wrote, "Hey guys! I just got back from day 2 of nationals and I'm sorry to say I am not moving on, nor am I in the top 60 of the country. Thank you from everyone for your support, and have a great rest of your summer and hope we can send some more guys to nationals in Kansas next year!"
Pierson was also a member of the Facebook group Smart Sundays, which according to the page is "for people who want to partake in discussions of politics, philosophy, religion and things of that nature."
On May 28, he posted a question to spark debate in the group: "I know it's not Sunday, but I was wondering to all the neoclassicals and neoliberals, why isn't the market correcting itself? If the invisible hand is so strong, shouldn't it be able to overpower regulations?"
Police say the shooting incident began about 12:30 p.m. and lasted about 14 minutes. Students huddled in closets and locked classrooms, carrying out the instructions that had been drilled into them since the shootings at Columbine.
Whitney Riley, a 15-year-old freshman, said she was walking into the study center with a group of friends. They were laughing and joking until "all of a sudden we heard a bang," she said.
She said everyone started running when they heard more shots. She finally ended up with eight other people, including two teachers, crammed into a tiny sprinkler system room. In those those moments, she said, she remembered all of the drills she had gone through.
"People were running through the halls, yelling, 'Get out, get out,'" she said.
Students in the sprinkler room said they heard someone urging them to come out but, as they were trained, refused to open the door because they did not know whether it might be the shooter seeking more targets.
Finally, one of the teachers said, "Let's go while we can."
As a group, they ran toward the exit. As Riley was running, she said, she saw two adults holding up a student who seemed to be injured in the leg.
John Spiegel, an 18-year-old senior, said he was in his psychology class on the north side of the high school when he heard a popping sound.
The sound brought the class to a halt, he said, and everyone began looking around, trying to identify it. Seconds later, there were three more rapid shots.
"It was clear as day. It sounded right outside the door," Spiegel said.
At the same time, he said, he heard what sounded like a student screaming, "We need help." Students in his classroom ran to the front of the room, turned off the light, and huddled together.
"We were just clumped together on the floor. It felt unreal," Spiegel said.
Blaise Potvien, 14, a freshman, said he was in his fifth-period class — U.S. history — when he heard three or four gunshots in the hallway.
"It was the loudest thing I ever heard," Potvien said at the nearby Shepherd of the Hills church. Parents rushed there to greet students who had left the school in an orderly march.
Seconds after the booming sounds, Potvien said, counselors and staff members were running down the hallway ordering everyone to close the classroom doors.
He said they turned out the lights in his classroom and hid in a far corner. Students were crying and screaming.
He said he texted his mother: "I love you mom and dad. Thank you for a wonderful life."
Teresa Potvien, his mother, said she was Christmas shopping when she got that text. "I almost threw up," she said.
This post has been updated to include additional interviews and incorporate information from past posts.
Times staff writer Saba Hamedy contributed to this report.