Authorities said the Colorado gunman, identified as Karl Pierson, had entered the facility armed with a shotgun, machete and three Molotov cocktails in his backpack, with the intent to harm a large number of people.
At a news conference on Saturday, Arapahoe County Sheriff Grayson Robinson said Pierson seems to have been motivated to retaliate against a teacher – thought to be librarian and debate coach, Tracy Murphy - when he entered the high school on Friday.
“It is our strong belief that he came to the school with that weapon and with multiple rounds … to cause harm to a large number of individuals. His intent was evil,” Robinson said.
Pierson was reportedly targeting Murphy because he had recently
removed him from the school’s debate team.
Pierson entered the building at approximately 12:33 pm and asked for Murphy by name. The student then proceeded to the library in search of the teacher, who was able to flee the building without injury. However, Pierson managed to hurt another person instead.
Claire Davis, 17, remained in critical condition on Saturday evening after authorities say she was shot at point-blank range by Pierson.
Pierson ignited one of the Molotov cocktails, and set fire to at least three bookshelves, investigators told KDVR.com. When an armed security guard entered the room, Pierson believed he was cornered and turned his gun on himself, Robinson said.
The entire attack lasted approximately 80 seconds and was captured by security cameras.
KDVR.com reports that a student at Arapahoe High School in Centennial said Pierson was in a "rage" on Wednesday and yelled at one of his teachers.
"Apparently that was enough to set him off," the student said.
The shooting took place about 10 miles from where Eric Harris and Dylan Klebold killed 12 students and one teacher in a rampage at Columbine High School in April 1999, before killing themselves.