The body of 41-year-old Rodeo resident Douglas Crossley II was found in the late morning or early afternoon in the area of Point Pinole Regional Park and Breuner Marsh, police said.
The case was initially reported to Richmond police, but East Bay Regional Park District police took over the investigation shortly after 1 p.m.
Davis said the autopsy indicated that Crossley died from blunt force trauma and appeared to have been beaten to death.
He was last seen alive at about 10 p.m. Saturday and appeared to have been killed where he was found, Davis said.
As of this morning, investigators had not identified any suspects or motive for the attack, Davis said.
Anyone with information about the case is urged to call East Bay Regional Park District police at (510) 690-6549. People who wish to remain anonymous can call the park district's tip line at (510) 690-6521.