It happened just before 8 a.m. in a small building next to an auto body shop at 2601 Westchester Avenue in the Westchester Village section.
The 63-year old father and his 38-year son were working in the basement. They told firefighters that the air compressor they were working with exploded.
Witnesses saw the building come crumbling down.
FDNY Fire Marshalls have determined that this was a natural gas explosion, however the source of that gas leak has yet to be determined and remains under investigation.
Juan Hernandez rushed to help and spotted the older man buried under layers of debris.
"I put my hand in to try and take him out, but he said he didn't want to come out, he wanted to wait for his son to come out first. He was really crying for his son," said Hernandez.
Both victims were taken to Jacobi Hospital with serious, but non life-threatening injuries.