School Shooter Scrawled Plan on His Arm The gunman who shot up a Colorado high school had scrawled an ominous Latin phrase on his arm along with a list of classrooms he planned to hit before he killed himself, Arapahoe County Sheriff Grayson Robinson said today. Five letters and numbers were scrawled in permanent marker on Karl Pierson's arm, along with a Latin phrase that translates as "The Die Has Been Cast," according to Robinson. The sheriff said investigators believe the letters and numbers on Pierson's arm corresponded to specific classrooms he planned to hit, but he said investigators were working to determine whether the shooter had specific targets in mind in those areas of the school. Last Friday, Pierson, 18, barged into Arapahoe High School in Centennial, Colo., armed with a shotgun and a slew of other weapons, including three Molotov cocktails, a machete and more than 125 rounds of ammunition, which Robinson said he wore in two bandoliers across his chest and waist. Pierson's apparent motive may have been "revenge" against the school's debate team instructor after he was kicked off the team, the sheriff said. During the 80 seconds of terror, Pierson set off an explosive device inside the school and fired five shots, according to police. Claire Davis, 17, was hit in the head and remains in the hospital in critical condition, according to a statement from her family. Police said they believe Davis was not intentionally targeted by Pierson. After 80 tense seconds, police said they believe Pierson realized that the school's resource officer was approaching, and Pierson shot himself dead in the library. "I believe the shooter knew that deputy sheriff's were immediately about to engage him, and I believe that shooter took his life because he knew that he had been found," Robinson said last week. Over the weekend, the sheriff said Pierson had legally purchased the 12-gauge shotgun at a Denver-area gun store on Dec. 6, and bought ammunition the day before his rampage.