A youth pastor in Colorado is facing charges of sexual assault after a young woman accused him of an "inappropriate" relationship that lasted seven years.

Boulder police spokeswoman Kim Kobel said in a news release obtained by KMGH that 35-year-old Jason Allen Roberson turned himself in on Wednesday after police issued a warrant for his arrest.

Roberson was a youth pastor at VineLife Church in Longmont, where he met his then-15-year-old victim in a church group in 2005. Police said that the youth pastor soon began calling, sending her text messages and showed up at her school.

Roberson had allegedly shown the girl a picture of his penis on his cellphone and said that he could not erase it. But he had said the had not meant for her to see it.

The girl told police that Roberson convinced her that she needed to change clothes because she was dressed inappropriately. She later learned that he had been watching her change clothes multiple times at her home and at the church. He had said that he could not help himself, court documents stated.

Roberson's behaviour eventually escalated from talk of masturbation to groping her breasts, according to the affidavit. Even after she "told Jason that she did not want him to touch her again," he eventually "resumed his attempts at sexual contact and emotional manipulation," the document said.

The girl finally moved on to another church and was convinced to press charges against Roberson. On March 15, 2013, the victim, who was now 23 years old, met with leaders at VineLife Church and they suspended Roberson from his youth pastor duties.

Church records obtained by detectives indicated that "Jason Roberson has repeatedly confessed to church officials that he has touched [the victim's] breasts on multiple occasions." The church also gave Roberson a lie detector test and he admitted that he fondled the girl before her 18th birthday. Under questioning from police, he agreed that he had touched her breasts, but he would not say if she was a minor at the time.

Roberson was arrested and charged with sexual assault on a child by a person in a position of trust, sexual exploitation of a child and unlawful sexual contact.

Kobel said that the incident was troubling because Roberson's victim "trusted him as an authority figure and spiritual guide, and felt uncomfortable disclosing the relationship to others."

Watch the video below from KDVR, broadcast Sept. 6, 2013.