Harrisburg, Pennsylvania high school student Asher Potts was a member of the National Honor Society and a lieutenant in the Navy Junior Reserve Officers Training Corps. But Asher was hiding a massive secret, one that would land him in jail.

Asher Potts was the kind of high school student any mom would be proud of. He was on the honor roll, had a chest full of medals from the Navy Junior ROTC, and he's articulate, leading a youth town hall against violence and drug dealers.

But there's only one problem: This model teenager is really an adult.

"Everybody is so surprised," said one student at Harrisburg High School.

Asher is an impostor. His real name is Artur Samarin, and he's a 23-year-old Ukrainian man.

It's almost like a scene from the classic television show "21 Jump Street," where baby-faced cops pretend to be students to catch drug dealers -- except Samarin wanted to grab a high school diploma.

Prosecutors say Samarin duped everyone during the four years he attended Harrisburg High School in Pennsylvania. And apparently no one was more fooled than the woman who brought him up like her own son, Stephayne Potts.

"I still don't believe he's 23, y'all gonna have to prove that to me," said Stephayne Potts. "Somebody's got to do something to prove that we watched this boy go from high-pitched tones to the way he speaks now, his shoe size, his clothing size, he got taller."

Now Samarin is going through his second puberty in jail. He was arrested on February 23 and locked up on multiple charges, including identity theft and statutory sexual assault.

Why did Stephayne change her mind about Samarin, who she considered family? She claims he was planning a violent attack on his school, and she turned him in to the FBI.

"He changed, he started talking about certain kids in the school that he wanted to hurt, and he talked about you know actually blowing the school up, and I said 'What?'" said Stephayne. "I was concerned about weapons. I was concerned he had started closing his door and he was talking to somebody in Russian."

How did a then-19-year-old from Eastern Europe pose as a 14-year-old to enroll in a high school in the first place? Dauphin County District Attorney Ed Marsico says he falsified the documents.

"Most of those require some type of parental involvement, so it became apparent they had to be involved in some of these situations," said Marsico.

School district officials didn't want to talk about the case to our Harrisburg affiliate WPMT-TV.

"There is a very active an ongoing investigation and the school district is not at liberty to speak at this time," said Harrisburg School District Spokeswoman Kirsten Keys.

The Potts say they met Samarin in 2012 when he and other Ukrainians were visiting Pennsylvania's capital city in 2012.

"His mother and grandfather wanted him to come to the United States to begin a new life, and they were trying to help him," said Potts family attorney Corky Goldstein.

Stephayne says they took him in after he showed them bullet wounds and knife scars he says he got as a child in Russia.

"He starts all this screaming, he's wetting the bed, he's in cold sweats," said Stephayne. "I told him a promise, no one will ever hurt you again."

Stephayne Potts and Artur Samarin reportedly exchanged texts after she turned him in.

"U want me change my name?" Samarin texted. Stephayne reportedly replies "Yes, this way I will never bother you again and you don't have to bother us."

Samarin spoke out from his jail cell, telling a local TV station it was Stephayne who came up with the idea to change his age. He claims he lived in what he calls a "slave driver" situation.

"It was only to help him," said Stephayne. "I wanted to help him have the best life he could possibly have."

Both Stephayne and her husband Michael deny Samarin's allegations and claim they believed him when he told them he was only 14. They have not been charged with any crime in connection with Samarin's alleged forgery.

"Everything Stephayne Potts says has to be taken with a grain of salt," said Samarin's attorney, Adam Klein.

Klein says they'll enter not-guilty pleas on all the charges.

But no matter what happens, Stephayne says she still considers him "her boy."

"He wanted to stay so we wanted to help him," said Stephayne Potts.