By DAN ELLIOTT and P. SOLOMON BANDA
A deputy of the Arapahoe County, Colo., Sheriff’s Department walks next to crime scene tape in front of a doorway to Arapahoe High School in Centennial, Colo., on Saturday, Dec. 14, 2013. The school was the scene of a shooting on Friday that left the student gunman dead and two other students injured. (AP Photo/David Zalubowski)
Arapahoe High School
Roses and a sign of support are woven into a cyclone fence around a tennis court at Arapahoe High School in Centennial, Colo., on Saturday, Dec. 14, 2013. The school was the scene of a shooting on Friday that left a student gunman dead and two other students injured. (AP Photo/David Zalubowski)
School Shooting
The front door at the Highlands Ranch, Colo., home of the 18-year-old shooting suspect Karl Halverson Pierson is covered with plywood on Saturday, Dec. 14, 2013, after the police searched the home. Pierson critically wounded one student, before apparently killing himself Friday at Arapahoe High School as police moved in. (AP Photo/Ed Andrieski)
Sean Sweeney
Sean Sweeney, a runner who lives near Arapahoe High School in Centennial, Colo., pauses to say a prayer for the victims and the gunman of a shooting at the school during his early morning run on Saturday, Dec. 14, 2013. The school was the scene of a shooting on Friday that left the student gunman dead and two other students injured. (AP Photo/David Zalubowski)
Michael Vartuli, Chris Davis
Michael Vartuli, left, and Chris Davis, both seniors at Arapahoe High School, hang a sign asking for donations for the victim of the shooting at the school in Centennial, Colo., early on Saturday, Dec. 14, 2013. Investigators were working to find out what motivated a teenage gunman to enter his suburban Denver high school armed with a shotgun looking for a specific teacher a day earlier. The 18-year-old shooter critically wounded a 15-year-old student and was later found dead in the school, apparently of a self-inflicted gunshot wound. (AP Photo/David Zalubowski)
APTOPIX Colorado School Shooting
Parents stand along the tennis court fence hoping to see if their child is standing outside on the football field after a gunman was spotted inside Arapahoe High School on Friday, Dec. 13, 2013, in Centennial, Colo. Authorities said the gunman shot two students and then turned the gun on himself. The shooting came a day before the anniversary of the Newtown, Conn., attack in which a gunman killed 20 children and six adults at Sandy Hook Elementary School. (AP Photo/The Denver Post, John Leyba) MAGS OUT; TV OUT; INTERNET OUT; NO SALES; NEW YORK POST OUT; NEW YORK DAILY NEWS OUT
School Shooting
Parents pick up their daughter at a church where students from nearby Arapahoe High School were evacuated to after a shooting on the Centennial, Colo., campus Friday, Dec. 13, 2013. Arapahoe County Sheriff Grayson Robinson said the shooter shot two others at the school, before apparently killing himself.(AP Photo/Brennan Linsley)
Colorado School-Shooting
A father picks up his daughter at a church where students from nearby Arapahoe High School were evacuated to after a shooting on the Centennial, Colo., campus Friday, Dec. 13, 2013. Arapahoe County Sheriff Grayson Robinson said the shooter shot two others at the school, before apparently killing himself.(AP Photo/Brennan Linsley)
Colorado School-Shooting
A parent picks up her daughter at a church where students from nearby Arapahoe High School were evacuated to after a shooting on the Centennial, Colo., campus Friday, Dec. 13, 2013. Arapahoe County Sheriff Grayson Robinson said the shooter shot two others at the school, before apparently killing himself. (AP Photo/Brennan Linsley)
Colorado School-Shooting
A woman screams as she arrives at a church where students from nearby Arapahoe High School were evacuated to after a shooting on the Centennial, Colo., campus Friday, Dec. 13, 2013. Arapahoe County Sheriff Grayson Robinson said the shooter shot two others at the school, before apparently killing himself.(AP Photo/Brennan Linsley)
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CENTENNIAL, Colo. (AP) — Authorities say an 18-year-old who wounded a fellow student before killing himself at a suburban Denver school entered the building with a shotgun, a machete and three incendiary devices in his backpack, and had ammunition strapped to body.
Arapahoe County Sheriff Grayson Robinson says Karl Pierson was motived by retaliation against a faculty member — probably a librarian — when he opened fire Friday at Arapahoe High School.
The sheriff says it appears the school librarian was the initial target but that Pierson planned to hurt multiple people.
Robinson says the librarian is leader of the speech team and Pierson was a member. He says the librarian disciplined Pierson in September but didn’t kick him off the team.
Robinson also says Pierson bought the shotgun legally Dec. 6 at a local store.
