The fire broke out in the 5000 block of McFadden Avenue shortly before 10:30 p.m. Friday.
Neighbors say they heard arguing right before the fire started, and saw someone leave the scene.
The victim has not been identified.
So far, investigators say they're still tracking down leads on a possible suspect. The fire was arson, and no arrests have been made, according to Santa Ana police.
The investigation is ongoing.