The gruesome discovery was made on the Nisqually Reservation, and on Sunday, investigators found even more body parts after one day of searching.
93-year-old Bill Flowers found the leg after his dog Liberty dragged it home, and was standing over it.
"I examined it," Flowers said. "I picked it up, and looked at the toes and nothing. None of the leg or foot was damaged - from the knee down it wasn't damaged at all."
Flowers said the leg was gray in color, and was dismembered about 4 inches from the buttocks.
He buried the leg in his backyard, and didn't call police until four days later - at the urging of his daughter.
"When I got home he told me, and I said, 'Dad we have to call the police'," Cheryl Flowers said.
Bill Flowers says he didn't report the incident immediately because he was scared he might be accused of murdering the person.
He said, "I was afraid to call. I'm 93 years-old. I didn't want to have to go to the pen for something I didn't do."
Detectives put a GPS collar on Liberty, hoping she would lead them to the rest of the body. But it was search and rescue dogs who found more remains - a pelvis and rib cage in the woods at the Nisqually Tribe's old fish hatchery.
Thurston County Coroner Gary Warnock said a pathologist will look at the remains to determine if it is a man or woman and what instrument or tools were used to dismember the body.