Before he entered the school, Karl Pierson wrote five sets of numbers and letters on his arm, which appear to correspond to Arapahoe High’s library and nearby classrooms.
Investigators are now working to figure out whether Pierson intended to target specific people in those rooms.
Pierson also inscribed a Latin phrase on the inside of his forearm, which translates to “The Die Has Been Cast.”
The investigator’s report also clarifies what happened during the 80-second attack.
According to the report, Pierson entered the school opening carrying as .12-gage shotgun and wearing 125 rounds of ammunition in bandoliers across his chest and around his waist.
He fired five times with his second shot hitting 17-year-old Claire Davis at point-blank range.
Davis remains in a coma in critical condition at a local hospital.
The attack ended when Pierson shot himself in the library of Friday.