Arapahoe High School gunman Karl Pierson scrawled messages on his arms pointing to five areas of the school he planned to attack, the Arapahoe County sheriff said Tuesday.

Also written on his forearm in permanent marker was the Latin phrase "Alea iacta est," which means in English "The die has been cast."

The letters and numbers on his arm correlated with specific classrooms located naer the school's library, where authorities have said Pierson planned to target librarian and debate coach Tracy Murphy.

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