In the shooting rampage, authorities say Pierson shot one student at the Colorado school before killing himself.
Pierson, who was an accomplished member of the school’s debate team, was reportedly on the hunt for the librarian, Tracy Murphy, reportedly screaming “Where’s Murphy?! Where’s Murphy?!” as he entered the building the school custodian, Fabian Llerenas, told the Daily News.
According to ABC 30, Pierson was carrying a shotgun as he searched the school for Murphy.
A student told the Daily News that Pierson went after Murphy because he had kicked him off the debate team.
Joe Redmond, 18, said Pierson had joked about killing Murphy, so the librarian had him suspended for the comment.
The student also told the Daily News Pierson wanted to enter the Air Force Academy and believed he would not be accepted due to the suspension. Thus Pierson apparently thought Murphy had “ruined his life,” Redmond said.
Once Murphy heard he was being targeted, he left the school, Arapahoe County Sheriff Grayson Robinson told ABC.
“He knew he was the target and left that school in an effort to try to encourage the shooter to also leave the school... That was a very wise tactical decision,” Robinson said.
ABC reports that the 15-year-old female student was shot is currently in critical condition.
Initially it was reported that two students had been shot, however, it was later learned that the other student was not injured, but had blood stains on her from the shooting victim.
Robinson noted that Pierson was found dead inside the school about 20 minutes after the shooting was reported.