A former Fairfax County firefighter and paramedic was sentenced Friday to 15 and a half years in prison for producing child pornography by screen-capturing online video chats with young children, according to authorities and court records.

Andrew Choi, 35, of Springfield, Va., had pleaded guilty in September to production of child pornography, admitting that he talked to at least 10 children whom officials were able to identify in online video chats, then used a screen-capture program to record them performing sex acts on camera. Investigators found about 600 such videos on his computer depicting boys under age 18, court records show.

Choi resigned from the Fairfax County Fire and Rescue Department, where he had worked since 2005, in January 2013, said Dan Schmidt, a Fairfax County Fire and Rescue spokesman. He was charged in the child pornography case a few months later, court records show.

Choi wrote in a letter to the judge in federal district court in Alexandria that he was “remorseful” for his actions and was “committed to addressing the root of my issues.” He wrote that he struggled with emotional problems and had been receiving therapy.

“I know that what I have done can’t be undone especially for my victims and their families,” Choi wrote. “I wanted to say that I am sorry, and that I accept full responsibility for my actions, and ask that you consider me a man who made some bad decisions in the past, but who recognizes this and has a strong commitment to change.”

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