TPM Livewire

Arapahoe High School Gunman Wrote Latin Phrase On His Arm

AP Photo

"The letters/numbers written on the shooter's arm is an indicator to investigators of the shooter's plan," Robinson wrote in a news release.

Robinson said investigators were now trying to determine if the occupants of the classrooms identified on Pierson's were targeted by the shooter. Authorities have said that Pierson planned to target librarian and debate coach Tracy Murphy, according to the Post. 

Pierson shot and wounded a fellow senior, Claire Davis, 17, on Friday, before killing himself in the school's library.