CENTENNIAL, CO, Dec. 14 (Xinhua) -- An 18-year-old high school senior who thought a teacher had destroyed his chances of attending the Air Force Academy has been identified by police as the lone gunman who wounded three students before taking his life at a suburban Denver high school Friday.
Karl Pierson was described by fellow students as a "good student," straight-laced, politically outspoken and verbally argumentative -- but not the type of kid to hunt down and try to kill a teacher.
Pierson died of a "self-inflicted" gunshot wound 14 minutes after barging into the school Friday afternoon carrying a shotgun, just as police were rushing to the scene.
Pierson, raised in an upscale Highlands Ranch neighborhood, was seeking revenge for being kicked off a debate team by targeting the teacher responsible, several students said in interviews following the incident.
In September, Pierson, who had dreams of attending the prestigious nearby Air Force Academy, was temporarily suspended from school for "jokingly" saying he wanted to kill the debate team coach Tracy Murphy, according to student interviews, which also noted that Pierson held conservative political views and championed "gun rights."
"He thought Mr. Murphy had ruined his life" with the suspension, said Joe Redmond, Pierson's friend and captain of the debate team. "(The Air Force) doesn't look positively on suspensions."
After entering south Denver's Arapahoe High School at 12:33 p.m. Friday, Pierson, dressed in military tactical gear and brandishing a shotgun, raced down the school's hallways screaming the name of the coach.
"Where's Murphy, where's Murphy?" Pierson yelled, according to eyewitnesses.
Students also described "smoke-filled" hallways created by an incendiary "device" that was also apparently ignited by Pierson.
Pierson found the Murphy, also the school's librarian, inside the school's library. Murphy barely escaped out a back door as the senior unloaded a shotgun blast over his head, sources said.
By the time police arrived at the scene a few minutes later, Pierson was dead and an unnamed, 15-year-old girl critically injured. She was airlifted to Littleton Hospital and underwent several hours of surgery Friday evening, according to sources.
"I believe the shooter took his life because he knew he had been found," Arapahoe County Sheriff Grayson Robinson said.
Two other students were treated for minor injuries and released.
Police say they also found another unexploded "Molotov cocktail " in the school.
By late Friday police had received and executed search warrants for Pierson's mother's home in Highland's Ranch, his father's home in Denver, and his car left in the parking lot of the school.
On Saturday morning, students returned to the school's student parking lot and began removing more than 100 cars left there since Friday morning.
The 2,229-student high school is likely to be closed until January, when school reopens after the holidays, officials said.
Officials say some 700 people have died from gunfire in this area south of Denver since the 1999 shooting at Columbine High School, located only eight miles away, where two student gunmen killed 12 before shooting themselves.