DENVER (CBS4) – A former Department of Education employee has been sentenced to 12 years in prison for taking pictures up the skirts of his female co-workers.

Thanh Ta, a budget analyst with the Colorado Department of Education, was found guilty of sexual assault, stalking, invasion of privacy for sexual gratification, and criminal attempt to commit invasion of privacy for sexual gratification.

He victimized numerous women at work, as well as hundreds of other unsuspecting women in public places.

Prosecutors say Ta took thousands of “upskirt” photos with his iPhone beginning in 2011, cataloging photos of his co-workers by name. Other, non-employee, names were listed in separate files.

Many of his victims showed up in court, hearing after hearing, to make sure their voices were heard.

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“Watching these women individually stand up to Thanh Ta was one thing,” said Asssistant Distirct Attorney Ryan Brackley. “But, seeing them sitting in court supporting each other was inspiring.”

Ta was finally caught when he connected a personal hard drive to his work computer at the Colorado Department of Education. Ta was placed on administrative leave and was later allowed to resign from CDE. But, police officers would examine his hard drives and found thousands of pictures, including evidence of a sexual assault.

Education personnel were able to retrieve approximately 250,000 files from the external hard drive, including most of the files deleted by Ta after officials had first discovered them.

Prosecutors say there were at least 135 victims, but received convictions for 12. The other charges were dropped because the statute of limitations had expired.