A hiker spotted a skull and a tennis shoe Sunday afternoon along a creekbed in a remote area of Shiloh Ranch Park in Windsor, said sheriff's Lt. Steve Brown.
The man, who was hiking with his two young children, called 911 at about 2:20 p.m. to report the finding.
Deputies confirmed the remains were human and secured the site until detectives can begin an investigation Monday morning.
"There's a full skeletal remains there," Brown said.
Other than the shoe, clothing wasn't evident, he said.
Shiloh Ranch Park, a Sonoma County regional park, is off of Shiloh Road and Faught Road, east of Windsor.