McALESTER, Okla. – Prosecutors have elevated to terrorism the criminal complaints against the former McAlester High School student accused of threatening a mass shooting with her newly acquired AK-47.

Terrorism can result in the maximum penalty of life in prison upon conviction.

Alexis Wilson, 18, of McAlester, was initially charged on Monday with perpetrating a terrorist hoax and endeavoring to perform an act of violence. They carry maximum prison sentences of 10 years.

District Attorney Chuck Sullivan increased the severity of the charges after reviewing the case with sheriff’s investigators who checked the contents of Wilson’s  iPhone. Wilson’s bail bond was also doubled to $500,000.

Sheriff’s deputies Sunday seized the AK-47 rifle, six ammunition clips, high-velocity bullets and a 12-gauge shotgun with a stock sleeve for extra shells from Wilson’s bedroom at a rural residence.

But investigators said in the court documents that they later found cellphone pictures of mass shootings, references to graduation crowds and dates, and texts saying she cut her hair to resemble one of the Columbine school shooters.

They also found messages on Wilson’s iPhone referencing the number of exits at the McAlester High School auditorium where graduations are held, potential dates for the graduation ceremonies, and text stating she would be “discovered” as the “next mass shooter.“

Sheriff’s deputies arrested Wilson Sunday night after receiving a report she showed a co-worker at a pizza restaurant photos of a recently purchased semi-automatic AK-47 rifle and saying she planned to kill “400 students for fun” at the high school. The co-worker told her manager, who notified authorities.

 “It was clear that there was more than simply a threat made,” said DA Sullivan. “She had motive, the means, and a definite plan to carry out the threat so we amended the charges.”

Wilson, who dropped out of high school as a freshman, appeared briefly in court Monday, pleading not guilty to the initial charges.

At her jail booking she wore a T-shirt referencing “The Anarchist Cookbook,” the 1971 tome advocating for violent civil disobedience that has been found among the belongings of school shooters.

Court documents included a Sept. 5 receipt Wilson purchased a Century Arms VSKA 7.62×39 AK-47 with a clip from a McAlester gun store in addition to five additional magazines and 160 rounds of high-caliber ammunition.

Pittsburg County Sheriff Chris Morris said Wilson bought the gun recently at a local gun store, passing a federal background check.

Details for this story were provided by the McAlester, Okla., News-Capital.