An Augusta man whose body was found along a road in Hallowell on Sunday was killed by an unknown person.

An autopsy Monday by the state Medical Examiner’s Office showed that the death of Paul Allen, 47, was a homicide, said Steve McCausland, spokesman for the Maine Department of Public Safety.

The cause of Allen’s death is being withheld at the request of the Attorney General’s Office. Police have not named a suspect.

Allen’s family expressed shock Monday at his death, and defended the man, who was convicted on four counts of sexual assault against a child more than a decade ago.

Allen’s body was found around noon Sunday a few yards off Winthrop Street in Hallowell, on a trail leading to granite quarries. McCausland said state and Hallowell police and the Maine Warden Service combed the scene until the early morning hours Monday.

Game wardens had been searching for Allen since Saturday afternoon, when his pickup truck was found parked on nearby Town Farm Road, McCausland said Sunday. Wardens using dogs found the body about a mile from where Allen’s truck was found. Investigators say Allen was last seen Thursday night at a toy auction at the Crystal Falls meeting facility in Chelsea.

Frank Doray of Augusta, Allen’s half brother, said Monday that he attended the auction with Allen. The men were in search of Christmas gifts, Doray said.

“I was the last person to see him alive,” he said. “He dropped me off from the toy auction.”

Doray said he sensed trouble when Allen didn’t answer his cell phone Friday and, later, when he missed an appointment.

“He was supposed to be somewhere,” Doray said. “He doesn’t miss things.”

Allen, who worked as a worm digger along the coast, was married and had four sons ranging from teenage to adult, Doray said.

After nearly dying more than a year ago from a brain aneurysm, Allen had begun working out.

Doray said that in 1978, his great-grandmother Emily Chase was killed in her home in Bowdoinham. Police have not solved that crime.

In 1997, a Kennebec County jury convicted Allen of two counts each of gross sexual assault and unlawful sexual contact. Allen was accused of molesting his live-in girlfriend’s daughter for two years, when she was 5 and 6 years old.

Allen was sentenced to 10 years in prison, with all but five years suspended and six years of probation.

Police are seeking the public’s help in finding out what happened to Allen. Anyone with information should call the state police at 624-7076.