A Maine couple whose son vanished without a trace in 1977 is wondering who would have sent them a letter recently claiming to have knowledge of the disappearance.

The unsigned letter has renewed police interest in the Bernard “Bunny” Ross Jr. missing persons case and dredged up old emotions for his parents, the Portland Press Herald reported Friday.

Ross was 18 and living with his parents in Fort Kent when he disappeared May 12, 1977. He walked out of the house, distressed over suspicion that he had stolen a vehicle, later found abandoned on a dirt road, the paper reported.

The letter postmarked in March was addressed to Carol Ross, 78, and her 80-year-old husband Bernard Ross Sr. at their home in Portland, according to the paper.

The writer claimed knowledge of their son’s disappearance and referenced a story that appeared in the Kennebec Journal. The article was about missing person cases and mentioned Bunny Ross, the Press Herald reported.

The writer also suggested that another story about the Ross case should appear in the paper, prompting police to arrange for reporters to interview the Ross parents Friday.

“I’ve never had anything like this happen in my career,” Maine State Police Lt Troy Gardner told the paper. “Basically, all we’re doing is extending an olive branch, saying we want to make contact with this person. Of course, there’s no way of knowing whether the letter’s truthful or the information is accurate, but we are asking for whoever wrote the letter to please contact us.”

Carol Ross told the Press Herald the only calls they’ve gotten after their son disappeared were from detectives around the country trying to identify a body.

“We’ve had several calls,” Carol Ross said. “You’d get your hopes up, but of course it would turn out to be someone else.”