An Oklahoma woman has been arrested after she allegedly threatened to "shoot 400 people for fun" at her former high school, CBS affiliate KOTV reports. Deputies with the Pittsburg County Sheriff's Office seized an AK-47 and a shotgun from Alexis Wilson, 18, who was charged Monday with making a terroristic threat.

Wilson was arrested after deputies got an anonymous tip that she told friends and coworkers she was going to shoot up McAlester High School, authorities said. They added that she had been posting videos of herself shooting guns.

One of the coworkers allegedly told the sheriff's office that Wilson threatened "to shoot 400 people for fun."

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"You know, it may not have been anything — we don't know 100%, but we are glad we got it before it turned into something," Pittsburg County Sheriff Chris Morris said.

Wilson had an AK-47 with six magazines and a 12-gauge shotgun with a stock sleeve for extra shells, according to Morris. He said Wilson picked up the AK-47 last week from a local gun shop with five extra high capacity magazines and 160 rounds of ammunition.

Wilson went to McAlester High School but dropped out in 9th grade, according to authorities. Wilson denied making threats to shoot up the school, but deputies said she admitted she'd been suicidal and borderline homicidal in the past and had thoughts of hurting people. She told deputies she was just trying to convince a coworker that not everyone who owns a gun is bad.

"In today's times, you can't say stuff like that," Morris said. "And anytime something is said like that we are going to take it serious. And we are going to investigate it to the fullest extent and make an arrest if possible because we do not want any of our schools getting shot up. Nobody does."

Similar concerns for school safety also led to the arrests of three students Sunday in California. The three teens were arrested for allegedly plotting a school shooting at Desert Hot Springs High School, which was thwarted by police, CBS Los Angeles reports.

Two boys and a girl were arrested Sunday and their homes searched after "troubling social media posts" were reported to the police. Detectives said they found a replica AR-15 and two real guns — a revolver and a semiautomatic black handgun — in their homes.

Officials said the replica AR-15 looked like a genuine weapon of war. "Tell you right now, officers encounter this at a school, out on the streets, someone jumps out of a car, points it at an officer — there's a high probability of a deadly confrontation," Detective Larry Gaines said. "There's no way to tell this a fake weapon without actually having it inside your hands."

The teenagers are in custody at juvenile hall and have been charged with making terrorist threats.