AURORA, Colo. -- A gymnastics coach is behind bars, accused of sexually assaulting a girl he was training, and now police are concerned there may be other victims from other gyms.

James Curtis Craig III, 35, was arrested Monday. Police said they've been investigating Craig since getting a tip from another law enforcement agency on Sept. 16.

"I run into this person all the time over here,” said Kiersty Mallory, a parent to three students in the dance academy next door. "It freaked me out. It just makes you wonder about everybody."

Craig is accused of inappropriately touching a teen girl during a training class at the Saddle Rock School of Gymnastics in Aurora between Aug. 7 and Monday.

"I do not understand that. We have people coming in here all the time. We have observation windows," said Tyler Salazar, owner of the gym and a friend of the suspect. "I just feel betrayed."

Craig has worked at Saddle Rock since it first opened in 2007. Police said he also may have coached at similar gyms across the Denver metro area.

Some parents told 7NEWS they had not heard about the arrest, including Jimmy Mindoro, who had dropped by to check out his 10-year-old son's new gymnastics coach for himself.

"You just want to do your double-check. You hear about things. Everyone goes (here). This was kind of new (for us). You kind of take things for granted but you've got to do a follow-up too," Mindoro said. "Because they’ll be working with your kids very closely."

According to state records, Craig was arrested in 2001 in Parker on charges of domestic violence and harassment. He pleaded to a lesser offense and received a deferred sentence.

He was also cited two months ago on a charge of indecent exposure in Centennial, records show. Sources told TheDenverChannel.com that his Aug. 21 arrest in Centennial is unrelated to the alleged sexual assault. An adult neighbor claimed she saw him standing and exposing himself in a garage as she drove by, according to sources.

Management at the Saddle Rock School said they used the Colorado Bureau of Investigation for Craig's initial background check two years ago and are now cooperating with investigators and assisting in the investigation.

"We have run background checks. We checked his references. Like I said, I've known him, he's coached for me, off and on for 10-12 years," Salazar said.

Craig is being held at the Arapahoe County Jail in lieu of $50,000 bond.

He faces investigation of sex assault on a child by a person in a position of trust and unlawful sexual contact.

If you have any information about this investigation or about Craig, call Detective Sue Wynn at 303-739-6208.