MESQUITE -- Police in Mesquite have arrested a youth pastor's assistant at a local church and charged him with sexually assaulting a child.

On Feb. 18, police received a report about the sexual assault. Their investigation concluded that Steven Winn, 33, had an ongoing sexual relationship with a teenager for just over a year. She was 15 when the relationship began and 16 when police got involved.

Police said Tuesday that Winn is the assistant youth pastor at Open Door Baptist Church in Mesquite. The victim was a student at the church's Christian school, police said.

Pastor Bob Ross with the church said Winn was never employed by the church and was a volunteer who served as an assistant to the youth pastor.

"Mr. Winn's primary duties consisted of helping to drive our teens to various activities such as camp, youth rallies, and summer camp," Ross said. "He had no official duties or title of any kind."

Police say Winn worked for the City of Mesquite as a construction inspector in the Public Works Department for 14 years. He was terminated on Feb. 20.

Two days later he was arrested and charged with three counts of sexual assault of a child in Dallas County. His bond was set at $25,000 for each count. A few days later he was charged with three counts of sexual assault of a child in Kaufman County. His bond there was set at $1,000 for each count.

Police say sexual encounters between Winn and the teen occurred in both counties. There were multiple occurrences in each, but prosecutors settled on three cases to charge, MPD said.