Fire officials say the man living inside the apartment on Leavitt Street was bleeding propane from a tank, which they believe sparked the explosion just before 7:30 p.m.
"We believe that the propane blew back through his back door into the house, an accumulation collected on the ground floor and at some point it hit an ignition point, causing the explosion," said FDNY Assistant Chief Edward Kilduff.
Witnesses told NY1 they felt the explosion a few blocks away.
"We were sitting in the house and all of a sudden felt the whole building shake. We felt the whole house shake like an earthquake," said a local.
"At first I thought it was a rumble of thunder but it's not the weather for it," said another local.
The resident whose apartment was destroyed suffered burns to his arms and face, and as of late Monday was in serious condition but expected to recover.
A woman who firefighters rescued from under debris suffered minor injuries.
The Red Cross was helping at least 10 displaced families Monday night. A city Housing Preservation and Development crew told the Associated Press that a demolition crew would demolish the house.
As fire officials labeled the explosion accidental Monday, no criminality charges are expected.