The case began as a missing person investigation, after a man called the Orange County Sheriff's Department Tuesday night, saying his mother was missing.
When deputies responded to the woman's home along the 27000 block of Cipres, they found the body of 69-year-old Marie Mosby.
On Wednesday, Charles Mosby, who is also Mosby's son but not the same man who called in the missing person report, was arrested on suspicion of murdering his mother.
Sheriff's officials say both suspect and victim resided in the same Mission Viejo home.
The son who originally reported his mother missing was not arrested and is not under investigation, authorities said.
The manner and cause of death have not yet been released. There are no other outstanding suspects or vehicles at this time, according to investigators.