The Cypress Police Department responded to a complaint about a man with a large knife running through a park at about 6:50 a.m. PDT, the Los Angeles Times reported.
CPD Sgt. Dean Pinvidic said officers saw the man enter a yard and then spotted a broken window in the house, suggesting he had broken in.
At some point, the house was set on fire. After firefighters put the fire out, investigators found the body of a man inside.
The man had not been identified by Saturday afternoon.
Pinvidic said the residents of the home were away at the time of the incident.