PROVIDENCE, R.I. — Louis James DeFusco was found floating in Narragansett Bay in 1964, a ship’s anchor tied around his legs and a bullet in his mouth. Authorities called it a suicide. But relatives had their doubts.

Some four decades later, family members had his body exhumed so it could be moved to a family burial plot. Before reburying the remains, they asked the medical examiner’s office to perform another autopsy.

The second examination this past summer revealed a bullet wound to the back of the head — a finding that changed the official cause of death from suicide-by-drowning to homicide. But who killed DeFusco remains a mystery.

“We didn’t want this thing to go on anymore, with the injustice of it being recorded as a suicide,” Robert DeFusco, who was 15 when his father died, said Wednesday.

Louis DeFusco was 38 when he disappeared the night of Aug. 6, 1964. Only hours earlier, the Cranston man was hitting golf balls in his yard with his son. He was last seen leaving a marina in Warwick, about 12 miles south of Providence, that he and his brother had just recently sold.

Twelve days later, his body was found floating in the water.

An initial autopsy found a bullet in the mouth and damage to his teeth, but did not spot a gunshot to the back of the head, said Dr. Thomas Gilson, the state’s chief medical examiner.

“He was not in the best of shape, apparently, when he was found,” said Gilson. “He’d been in the water for a period of time, maybe as much as 12 days, and it was overlooked.”

Robert DeFusco, now 57 and retired in Dover, Mass., said he and his sister planned earlier this year to move their father’s remains from one plot in a Cranston cemetery to another. But first they wanted his corpse re-examined.

The youngest of six children, and an entrepreneurial son of Italian immigrants, Louis DeFusco was considered a hardworking businessman.

At the time of his death, he was in the process of divorcing his wife, with whom he had three kids. Authorities looked into several theories, even questioning his estranged wife before ultimately settling on suicide.

“He wasn’t despondent, none of the things that would indicate he would be suicidal. It just wasn’t him,” said Robert DeFusco, who lived with his father and chipped golf balls with him on the day of the disappearance. Two other siblings lived with their mother.

Plus, there were the peculiar circumstances: the heavy anchor tied around his legs and the curiously undetected gunshot wound to the head.

Authorities who investigated the death in 1964 determined that Louis DeFusco had drowned himself.

After the first autopsy failed to find the entrance wound, Gilson said, doctors must have inferred that DeFusco shot himself in the mouth, survived, and drowned by attaching an anchor to himself. The gunshot wound identified in the mouth was initially thought to be nonfatal.

“The anchor sort of has a different implication now that we have a gunshot wound to the back of his head,” Gilson said.

He said DeFusco’s body was preserved well enough after burial to clearly reveal the fatal head wound.

The medical examiner at the time, Dr. Harold Beddoe, was quoted in The Providence Evening Bulletin as saying there was no evidence of a homicide or truth to rumors he had been “killed for reasons relating to his private life, business connections, alleged gambling debts, or during the course of a robbery.”