SAN DIEGO - A suspect was in custody on Tuesday in connection with the slaying of a 20-year-old man whose badly burned body was found four months ago in the trunk of a torched sedan on a back-country road in Jamul.

Miles B. Sharp, 21, is expected to face charges of murder and arson in the death of one-time 4S Ranch resident Dillon Davis, according to sheriff's officials.

Authorities have withheld Davis' cause of death and have disclosed no suspected motive for the killing. Detectives told 10News that Sharp and Davis were acquaintances.

It was unclear where the victim lived at the time of his death, though he had relatives living on the East Coast, homicide Lt. Glenn Giannantonio said.

Sharp was in jail in Humboldt County in an unrelated case when sheriff's detectives arrested him Friday on suspicion of murdering Davis, the lieutenant said.

10News learned Sharp was arrested in Vista on Oct. 15 on suspicion of robbery and assault in connection with an incident at a Humboldt State University dormitory, where a resident was bound and beaten by four men. Sharp was named as one of the suspects, was arrested in Vista and then transported to Humboldt County.

A Humboldt University website said that when Sharp was a freshman in 2009, he played wide receiver on the school's football team. The website said Sharp was from Spring Valley and had attended Mt. Carmel High School.