Before he stepped foot into Arapahoe High School on Friday, Karl Pierson scrawled a Latin message on the inside of his forearm in permanent ink. Translation: "The die has been cast." 
 
 Also written on his arm were numbers and letters associated with five classrooms and the school's library, places authorities said Pierson planned to attack during his noon-hour rampage, Arapahoe County Sheriff Grayson Robinson said Tuesday. 
 
 The sheriff offered new glimpses into what he described as Pierson's plan to harm many. 
 
 "And I believe it was a plan," Robinson said, adding that the numbers and letters on the gunman's arm were "to remind him where he wanted to go." 
 
 Karl Pierson (via Karl Pierson's facebook profile) 
 
 Before killing himself inside the library, Pierson, 18, shot and critically wounded fellow senior Claire Davis, 17, who on Tuesday remained hospitalized in a coma. 
 
 The sheriff has said Pierson was targeting his debate coach and librarian, Tracy Murphy, when he came to school armed with a 12-gauge pump-action shotgun, three Molotov cocktails and a machete concealed in a canvas scabbard. 
 
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 But those weapons, along with more than 125 rounds of assorted ammunition he wore in a pair of bandoliers strapped to his chest and waist, are a sign he wanted to wound more than just Murphy, Robinson said. Pierson packed a mix of steel-shot, buckshot and slugs, but the sheriff would not say which of those he fired. 
 
 "The shooter was intent on causing the maximum amount of harm," Robinson said. He would not elaborate on what other evidence had been gathered by investigators, but he said they still had a great deal of work ahead of them. The FBI is helping with the "methodical" and "complex" probe. 
 
 Their goals include determining the relevance of the classroom numbers and whether anyone inside them was also a target. 
 
 As for the Latin message on Pierson's arm, "Alea iacta est," Robinson said "it pretty much speaks for itself." The sentence is a line attributed to Julius Caesar, who said the words as he crossed the Rubicon river with his troops to start a civil war. 
 
 "It's indicating that things have been put in motion and won't be stopped," Robinson said. It appears Pierson acted alone, but the sheriff's investigation will determine whether anyone helped him. 
 
 Pierson, who turned 18 in September, bought the shotgun legally on Dec. 6 from a local sporting goods store and purchased the ammunition last week. 
 
 Police said he entered the school from the north side and fired randomly down a hallway before shooting Davis in the head at point-blank range. She was sitting in the hallway with a friend and had no time to react. 
 
 He then moved to the library, as a sheriff's deputy acting as a school resource officer closed in. Murphy, knowing he was sought, escaped the library with the help of a school janitor. Robinson would not elaborate on his exit. 
 
 Pierson fired a total of five times and ignited a Molotov cocktail that set ablaze three bookshelves in the library. He then fatally shot himself in the head, about 80 seconds after he entered the school. 
 
 "I heard him say, 'Where's Murphy? Where's Murphy?' " between gunshots, said senior August Clary, who was sitting in science class when the school went on lockdown. 
 
 Tait Priser, who graduated last year, said he was chatting with a teacher down the hall when he heard a gunshot and saw Pierson, whom he did not recognize, wearing a hooded sweatshirt and aiming the shotgun in their direction. 
 
 "I looked, saw him reload and dove into the atrium," he said. "He wasn't running, he wasn't yelling. He was calmly walking. It just seemed like it was an everyday occurrence for him." 
 
 Robinson said Pierson had been nursing a grudge against Murphy and had made a verbal threat against him in September that resulted in disciplinary action. Students have said Pierson and Murphy had ongoing confrontations about issues on the debate team. 
 
 Pierson's father, Mark, told The Denver Post that he and his ex-wife attended multiple disciplinary hearings with school officials earlier this year. 
 
 The new information came as staff members prepared to return to the school to gather their belongings Wednesday. Students will be allowed to do the same Thursday. The district said classes and final exams won't resume until after winter break in January. 
 
 Sadie Gurman: 303-954-1661, sgurman@denverpost.com or twitter.com/sgurman 
 
 Staff writer Jordan Steffen contributed to this report. 

 A student who killed himself in a violent attack at a Colorado school had apparently intended much more carnage 
 
 Arapahoe High School junior Emily Evans, right, and her mother Cristina hug while visiting a makeshift memorial bearing the name of wounded student Claire Davis, who was shot by a classmate three days earlier, in front of Arapahoe High School in Centennial, Colo. (Photo: Brennan Linsley, AP) Story Highlights Police: Shooter may have planned to attack several classrooms 
 
 17-year-old victim Claire Davis remains in critical condition 
 
 The teen who launched Friday's shooting spree at a suburban Denver high school was armed with 125 rounds of ammunition and three incendiary devices and may have planned to attack people in numerous rooms throughout the building, local authorities said Tuesday. 
 
 Arapahoe County Sheriff Grayson Robinson said Tuesday that before entering Arapahoe High School, 18-year-old senior Karl Pierson had written the Latin phrase "Alea iacta est,'' which means "the die has been cast" on his forearm, as well as letters and numbers that are linked to the school library and four classrooms. 
 
 Pierson, armed with a pump-action shotgun recently purchased at a local sporting goods store, entered the school at about 12:30 p.m., seeking a school librarian and debate team manager who was his intended target. After the librarian was alerted and fled the building, Pierson shot classmate Claire Davis at point blank range in the head before taking his own life. 
 
 Davis, 17, remains in critical condition at Littleton Adventist Hospital. 
 
 Robinson said Pierson entered the building with three types of shotgun shells, including buckshot and slug rounds - some in bandoliers slung around his chest and waist. He also carried three "functional'' Molotov cocktails and a machete in a backpack. 
 
 
 
 Pierson managed to fire just five rounds before turning the weapon on himself as a school resource officer closed in on the school library. The incident last just 80 seconds. 
 
 Police said the phrase and numbers and letters written on Pierson's arm are an "indicator to investigators of the shooter's plan." 
 
 Investigators are trying to determine whether Pierson planned to attack specific students and staffers in the classrooms and library and if he had help. 
 
 Arapahoe High students are scheduled to resume classes Thursday. 
 
 Contributing: KUSA-TV in Denver. 
 
 
 
 
 
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– Colorado student Karl Pierson walked into his high school intending to kill a lot more people than just the debate coach who kicked him off the team, chilling new details suggest. Investigators say the 18-year-old entered Arapahoe High School with 125 rounds of ammunition, three incendiary devices, and letters and numbers written on his arm that corresponded to five locations inside the school, USA Today reports. He had also written the Latin phrase "Alea iacta est"—"The die has been cast"—on his forearm. Pierson, who was armed with a shotgun he bought legally, "was intent on causing the maximum amount of harm," and the Latin phrase, attributed to Julius Caesar as he crossed the Rubicon, indicates "that things have been put in motion and won't be stopped," the local sheriff says. But despite the plan, Pierson was dead within 80 seconds of entering the school. The classmate he shot, 17-year-old Claire Davis, remains in critical condition and classes at the school will not resume until next year, reports the Denver Post.