Officials say the two-alarm fire broke out at a home near 15th street and Massachusetts Avenue. Arson investigators with the San Bernardino Fire Department sifted through burned rubble searching for clues.
Neighbors usually help take care of the man. They put him to bed Sunday night, then they woke up to the house next door fully engulfed in flames.
"There was a loud pop, and that woke me up, and I seen all the smoke, then we ran out the house," said Alex Burk, a San Bernardino resident.
Area residents say they tried to save the man, but the heavy smoke and flames kept them from reaching him.
"When units arrived on scene, they found a well-involved structure. They initiated an aggressive fire attack as well as a search at the same time, because we did have confirmation that there was a victim inside the structure," said Mike Arvizo with the San Bernardino Fire Department.
Neighbors say the elderly man, who went by the nickname "Cowboy," lived alone and was disabled. Firefighters found the man's body in a back bedroom.
The cause of the fire remains under investigation.