"Detectives located what appeared to be a dismembered human corpse in the rear yard," said San Bruno Police Chief Ed Barberini.
Stubblefield is now facing a long list of charges.
"Murder, robbery, burglary, the unlawful possession and use of tear gas and being a felon in possession of a firearm," said Barberini.
The police chief says a portion of the body was outdoors and another a portion of it inside a structure.
FULL VIDEO: San Bruno police hold news conference about dismembered body
FULL VIDEO: San Bruno police give update on dismembered body
Investigators were at Stubblefield's home as part of a continuing missing person investigation that someone reported last Wednesday.
Neighbors tell ABC7 News the missing man is approximately 70 years old and lives in a home on the same street at Stubblefield.
"He wore a cowboy hat and that's all that I really knew of him. It's just really sad to hear that he's still missing and they don't know if that's him that they found up the hill," said neighbor Mary Wahed.
San Bruno police say the missing man and Stubblefield were acquaintances.
The coroner has not yet identified the dismembered body found at Stubblefield's home.
"To be clear, the missing person case originally filed with our department is still an open investigation and is not closed due to yesterday's developments," Barberini said.
Wahed added, "To hear a life is taken on your street is just disheartening and sickening at the same time."
By phone, Stubblefield's relative also said he was sickened. He described Stubblefield as being a bit off and said he worked in IT. He also said Stubblefield told family members he had pancreatic cancer and not much longer to live.
San Bruno police say Stubblefield had a criminal history but did not say what.