JACKSONVILLE, Fla. – A former Jacksonville middle school teacher accused of sexting minors changed his plea to guilty last week and was sentenced to three years in prison.

Kristopher Paul Beckstrom, who taught music at Landon Middle School, posed as a 15-year-old boy and exchange sordid photos with children, authorities said.

Beckstrom was given credit for 337 days served and must register as a sexual offender.

He will be on sex offender probation for three years after he serves his sentence. As part of his probation, he has to complete psychosexual counseling, can't have unsupervised contact with kids under 18, and can't live within 1,000 feet of a school/day care where children congregate.

Duval County Public Schools told News4Jax that Beckstrom is not longer a teacher with the school district, as he had resigned Sept. 20, 2018, which was the day after his arrest. 

According to Beckstrom's arrest report, a teen came forward Sept. 13, saying a user named "erikb20172018" had been sending her "random" requests for nude photos on Instagram and Snapchat.

She told police she ignored the messages until another user messaged her on Instagram Sept. 10 with a screenshot of the "erikb20172018" profile and a note that said: "He is not who you think he is."

The other user said she too had been messaged by "Erik" in the past. But she thought it odd that he avoided sharing live videos with her and that the photos he shared didn't match his profile picture.

Confronted with these suspicions, the other user said, "Erik" told her that he was Kristopher -- a 42-year-old music teacher at Landon Middle School who was married with children, according to the report.

The victim told police the other user's description of sounded like her former teacher, too. She said he was described as a heavier-set, older, white man with distinctive facial hair.

According to police, the victim also reported that Beckstrom once indicated he took underwear out of a female student's bag that had been left behind in his class.