It happened at the Saint Andrews Apartments in Mariposa around 5:30 a.m. This video shows some of the damage left behind.
Cal-fire and Mariposa County Fire crews were able to get to the apartment quickly because they have stations nearby.
When they arrived, 67-year-old Ron Wallace was still inside.
Firefighters rescued him from the burning unit, but he had to be flown to a Fresno hospital with second and third degree burns.
"Ron's a really nice guy. He really is, and he's a non-smoker, so I have no idea what happened, we just hope the best for him," Carol Graychik said.
Investigators are still searching for the cause of the fire. Crews kept the flames from spreading to other units.
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