An autopsy was being conducted Friday morning on a beheaded, burned corpse found on a cul-de-sac about 20 miles northwest of Detroit and identified as a 26-year-old convicted sex offender.

Police are searching for a burgundy Chevy S-10 pickup truck belonging to the victim, Daniel Gene-Vincent Sorensen, 26, of River Rouge, Mich., after state police used fingerprints to identify the body.

"We believe it's an isolated incident," said Det. Lt. Michael Wildt of Northville Township Police. "We have to find out who did it, why and where did it happen. This is where we found the body, but we don't believe the person was murdered there."

Sorensen had been convicted of the criminal sexual abuse of a teen between the age of 13 and 17 in Tazewell County, Ill., according to that state's sex offender registry. But investigators weren't sure if that had anything to do with his brutal death.

"As of right now we don't have anything that says it is; we don't have anything that says it isn't," Wildt said. "We don't know."

The body was found Thursday morning by Northville Township public works employees along a road in Hidden Ridge, a subdivision under development. The body was set on fire Wednesday night between 7:30 p.m. and 10:30 p.m., police said.

"It burned for a long time," Wildt said.

Sorensen's head has not been found and a cause of death has not been released.

"Who would do something like this to my son?" his father, Jim Sorensen, told MyFOXDetroit.

Click here to watch the MyFOXDetroit report.

Sorensen worked odd jobs doing construction and landscape work, police said. He was last seen alive on Wednesday.

His pickup truck has the Michigan license plate BBV 9503.

FOXNews.com's Sara Bonisteel contributed to this report.