The 53-year-old allegedly "befriended" the 21-year-old victim and took him into a dressing room Feb. 1, police wrote in a news release Tuesday.
Surveillance video showed the two emerging about three minutes later.
The victim's mother, Teresa Emery, said her son rejoined her at the cash register with the man after she asked store staff to page him over the loudspeakers. Over his clothes he was wearing white coveralls designated for LDS temple wear, she said.
"He can barely dress himself on his own," Emery said. "[The man] basically had to force him to do that."
When the man offered to pay for the jumpsuit at the cash register, Emery tried to take it off her son. When she unzipped it, she said, the man intervened.
"He zips it back up and buckles it . . . right in front of me," Emery said. "He says, 'I want to buy this for you.' . . . He hugged him and told him he'd see him again, that he loved him."
Emery said she had never seen the man before. The man returned to the dressing rooms to search for a cell phone before leaving the store, she said.
Emery said she takes her son to the store regularly, and workers there know him well.
Emery said she returned with her husband to discuss the incident with store managers and call police. When officers arrived, the man appeared in the store parking lot, wearing his own white jumpsuit under a trench coat and a hockey mask on his face. Police arrested him and are seeking a charge of unlawful detention.
Emery said her son cannot communicate what happened in the dressing room.
"He gets upset," she said. "When we mention the man from D.I., he cries."
Police wrote there is no evidence of sexual assault.