It happened inside a two-story private house on West 234th Street in the Kingsbridge section just after 7:30 a.m. Tuesday.
Battalion Chief Michael Fahy, a 17-year-veteran with Battalion 19 in the Bronx, was evacuating the house at the time and was struck by debris from the explosion.
He was rushed to New York Presbyterian Hospital-Allen Pavilion, but could not be saved.
PHOTOS: Explosion in the Bronx
"He was a star, a brave man," said FDNY Commissioner Daniel Nigro of Fahy, a married father of three.
"It's a terrible loss for the Fahy family, a loss for the fire department family," said Nigro. "We feel it deeply today."
Nine firefighters sustained non life-threatening injuries. Also injured were six police officers, three Con Edison workers and two civilians.
Eyewitness News obtained this exclusive video showing the aftermath of the scene. You can see firefighters trying to help Fahy, and then the debris from the roof of the house that struck and ultimately killed him:
At 6:22 a.m., firefighters responded to a gas leak in the house. At some point, an illegal drug lab was detected and police were called.
Police revealed that for two weeks, they'd already been investigating the home, after neighbors reported what looked like drug activity, and a steady stream of fancy cars.
The gas line to the house was capped by firefighters up to 45 minutes before the explosion. Investigators are looking at other options connected to growing marijuana to determine what caused the blast.
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"Our members were investigating an odor of gas, he was directing operations," said Nigro. "They evacuated the surrounding buildings, got everyone else out of the way, when the explosion occurred."
Video from NewsCopter 7 over the scene:
The single-family house was partially destroyed and the explosion rocked an area of row houses in Kingsbridge.
Amid reports that a man was spotted fleeing the neighborhood after the explosion, police picked up the home's official renter in Jersey City Tuesday afternoon.
Though, the charges against him weren't immediately clear, detectives in the Bronx have questioned several other people as well.
Police Commissioner James O'Neill says part of the investigation will involve looking into the location as a possible marijuana "grow house."