The owner was doing renovations and landscaping Tuesday when he found a shallow grave, KSAZ-TV, Phoenix, reported.
Police and forensic specialists are now working meticulously to unearth the remains, KSAZ-TV said, and about 10 p.m. Tuesday, lifted a large wooden box from the hole.
Neighbors told KSAZ-TV the previous owners of the home were violent and not friendly.
The residence was the scene of a standoff with a police SWAT team last March, The Arizona Republic reported, and the resident, Alan Champagne, was accused of shooting at officers during the incident.
Champagne is now facing a number of charges, including first-degree murder, the Republic said.