The student who opened fire at his suburban Denver high school last week apparently planned to attack at least five different areas, investigators said Tuesday.
Letters and numbers corresponding to the locations of the Arapahoe High School library and four adjacent classrooms were written in indelible marker on Karl Pierson's arm, and investigators believed he planned to target those spots, Arapahoe County Sheriff Grayson Robinson said in a statement.
Investigators were trying to determine if the occupants of those rooms may have been personally targeted by Pierson.
Robinson has previously said that investigators believed a librarian who headed the school's speech and debate team was Pierson's intended target Friday, but he also planned to harm many others. The librarian escaped, but Pierson critically wounded a 17-year-old senior, Claire Davis, whom he encountered soon after entering the school armed with a 12-gauge pump-action shotgun, a machete and three Molotov cocktails.
Davis was sitting with a friend near the school library when Pierson shot her in the head point-blank. She remains in a coma.
Pierson ended up killing himself in the library with his sixth and final shot 80 seconds after entering the school, as a school resource officer was closing in.
Robinson also gave more details Tuesday about the amount and type of ammunition Pierson carried — more than 125 rounds of steel-shot, buckshot and slug ammunition.
Also written on Pierson's arm was the Latin phrase "Alea iacta est," which translates to "The die has been cast."