A troubled teenage girl from Oklahoma was accused Monday of threatening to “shoot 400 people for fun” at her former high school — and police said they found an AK-47 at her home.

Alexis Wilson, 18, made the chilling statement to a coworker at a pizza shop in McAlester, Okla., and showed a second person multiple videos of her shooting her newly purchased assault rifle, the Pittsburg County Sheriff’s Office said, according to Fox23.

Authorities said Wilson was expelled from McAlester High School over violent incidents and had previously been suspended for being caught with a knife. She wasn’t allowed to re-enroll.

Deputies on Sunday found the weapon, along with six magazines and a 12-gauge shotgun with a stock sleeve, in Wilson’s room at her home.

When confronted, Wilson allegedly told deputies that she “would never shoot up a school” and that her coworker had misunderstood, the McAlester News-Capital reported.

Wilson explained she was trying to convince her fellow employee that not all gun owners are bad people, deputies wrote in an incident report.

She agreed to show the cops the cellphone footage of her shooting guns — but became nervous and said she had some disturbing and “criminal-like things” on the device, according to the report.

Wilson allegedly told them she used to be suicidal and “borderline homicidal to the people of McAlester school because she was bullied.”

The girl’s mother said her daughter had been saving up for the rifle, which didn’t worry her because “Alexis has always shot firearms and had hunted.”

A mugshot released by the sheriff’s office shows the stoned-faced brunette in a black “The Anarchist Cookbook” shirt, a reference to the incendiary 1971 manual for civil disobedience.

The teen was charged with felony terrorist hoax.

Wilson was held at the Pittsburg County Jail on $250,000 bond. Her next court date is scheduled for Sept. 27.

McAlester Public Schools Superintendent Randy Hughes said Monday he asked for extra security at the high school.

“We’re having school,” Hughes said. “We went through this last year when we had a threat and it’s the same thing — added security, extra police officers.”

With Post wires