GARDEN CITY, N.Y. ? Willie Hayes was a Vietnam veteran who proudly served his country, won several medals and earned himself a plot at a veterans’ cemetery upon his death two weeks ago.

But there was one problem: As far as the U.S. government was concerned, it buried Willie Hayes nearly four years ago.

An apparently homeless man who went by the name Willie Hayes and had the same Social Security number, military record and date of birth was laid to rest at the cemetery in 2003.

The family of the recently deceased Hayes was stunned to find out about the apparent impostor, and cemetery officials are asking some perplexing questions, among them: Did the man in the grave steal Willie Hayes’ identity? Was it a clerical error?

“If he didn’t serve in the Army, he shouldn’t be there. It’s not fair to the veterans. He stole my brother’s identity,” said Hayes’ brother, Sylvester.

This much is certain: The Willie Hayes who died two weeks ago at 59 served in the Army in Vietnam, earned several medals and worked at a printing business. His family provided cemetery officials with overwhelming documentation of his military service and identity that show he is the rightful owner of a plot at Calverton National Cemetery.

But little is known about the other Willie Hayes.

He was buried on Christmas Eve 2003 in the Long Island cemetery, two months after dying in a Bronx nursing home. No one came forward to claim his body, and the nursing home staff believed he was homeless. A spokesman for the center did not return a call for comment.

“I’ve got 200,000 people buried here, but I’ve never seen anything like this,” Calverton director Michael Picerno said. “Ninety-nine percent of the time, the family has all the information, all the documentation, so these things never happen.”

Officials are exploring several scenarios in trying to solve the mystery.

One is identity theft: The man who died in 2003 could have simply stolen Willie Hayes’ personal information and went to his grave as an impostor.

Another is that the man in the grave really was named Willie Hayes but his Social Security number and personal information somehow got mixed up with those of the other Willie Hayes.