AURORA, Colo. — A former Aurora taekwondo instructor was sentenced Friday to 50 years in prison for filming children in changing rooms.

Erik Chen, 32, pleaded guilty to three counts of sexual exploitation of a child in March. He previously worked at Han Lee’s Taekwondo Academy in Aurora.

According to the 18th Judicial District Attorney’s Office, in February 2021, a father reported to Aurora police that his two daughters found Chen’s cellphone, which was recording them, while they were changing clothes in the Lone Tree Recreation Center’s changing room. The girls indicated that they deleted the videos, the district attorney’s office said.

Aurora police took a report, but there was not enough probable cause or evidence to make an arrest at that time, according to the district attorney’s office.

In June 2021, a therapist told authorities one of her clients disclosed that they were recorded by Chen in the restroom of the Castle Rock Recreation Center in 2020.

Investigators learned Chen ran summer camps for the taekwondo center, which has locations in Aurora in Lone Tree. Chen would leave his backpack in a changing room or restroom with his cellphone recording in a side pocket, the district attorney’s office said. On one occasion, a victim spotted the phone and went to turn it around out of precaution when they found it was recording.

Authorities executed a search warrant for Chen’s home and electronic devices in August 2021. Multiple computers, CDs and DVDs were seized, the district attorney’s office said.

Investigators found “hundreds of thousands of images of child pornography depicting girls believed to be between the ages of 8 and 12” on the electronic devices, according to the district attorney’s office. Detectives also found more than a half dozen videos Chen took in local bathrooms or locker rooms. Young girls and one boy are seen changing clothes in the videos, according to the district attorney’s office. On some of the videos, Chen is seen setting up the phone to record.

“This defendant preyed on innocent, young children who trusted him as a camp leader,” Senior Deputy District Attorney Zoe Laird said in a statement. “I hope this sentence provides some sense of closure for his victims and at a minimum, it ensures the defendant won’t be able to victimize and exploit other children in our community while he serves his sentence in prison.”

Chen was sentenced Friday to 50 years in prison. After his release, he will be required to register as a sex offender.