WATERVILLE — The executive director of the Mid-Maine Homeless Shelter in Waterville said her staff did background and security checks before hiring a Fairfield man now charged with possession of child pornography.

Thomas Williams, 68, was arrested July 25 after an investigation by the Computer Crimes Unit of the Maine State Police. He is charged with possession of sexually explicit material of someone under the age of 12. The crime is a Class C felony.

State police said in a news release Monday that none of the images was of Maine children.

Shelter director Betty Palmer said Friday that Williams was employed as a night-shift attendant at the shelter at 19 Colby Circle. Families with children can stay in the shelter, which includes 24 beds in the family units and 24 beds for single men and women. The shelter also offers portable cribs and toddler beds for infants to 3-year-olds.

“It took me quite by surprise,” Palmer said of Williams’ arrest. “We were told there were no local children involved. We did the obvious background checks we do as an employer, along with reference checks and we got nothing – not a hint that there might be anything wrong with his employment with us.”

Lt. Glenn Lang, head of the Computer Crimes Unit, said police investigators, acting on a tip, found sexually explicit images of children under 12 on Williams’ home computer. He said it is especially troubling when someone charged with child pornography crimes has access to families with children who are already in a vulnerable situation.

The concern “is when someone who has this material has access to a more vulnerable group, whether it’s children or a family in a shelter situation – those are just very vulnerable people.” Lang said. “I think it’s easier for people to take advantage of vulnerable people.”

Palmer said she and her staff reviewed the shelter’s security tapes – the entire building is under surveillance at all times – and found no illegal contact with children at the shelter. The shelter’s computers are being checked to see if there was any illegal activity online there.

“Minors and children have to be supervised by their parents; we don’t have any children without parents in the shelter,” Palmer said. “We’re as sure as sure can be that everybody in our shelter was safe without incident. We have some good policies in place that seemed to have been followed by all of us.”

Palmer said the job of a night-shift attendant is to monitor activity when people get up at night, to call an ambulance if one is needed, and to perform custodial cleaning, but always with another staff member or volunteer in the building.

“He’s never been arrested before,” she said. “There’s no way to know about someone even with references and full background check.”

Palmer said Williams quit his job the week before his arrest, but no one knew why. She said Williams came to work at the shelter with good credentials, having worked for years at several reputable social service agencies.

“I knew him from homeless prevention work in the community before he worked at the shelter,” she said. “The shelter is a safe place. We don’t want families to think it’s not safe here and sleep in their cars at night.”

Williams was freed on bail. He is scheduled to make his first appearance in court Oct. 10.