Fellow firefighters are remembering the FDNY Battalion Chief killed in a  house explosion in the Bronx Tuesday morning as investigators question a man who had rented the home. Law enforcement sources are telling NY1 they now believe it was a gas explosion, possibly linked to the growing of marijuana. Bronx reporter Erin Clarke has more.

Though they were solemn as memorial bunting was draped across the Battalion 19 firehouse in honor of 44-year-old Chief Michael Fahy, firefighters who knew him best smiled through their sadness remembering a man they called a brother.

Lieutenant John Paul Augier and Captain Brendan Deehan came up in the department with Fahy.

"Mike Fahy was the nicest guy of all the nice guys that anyone has ever met," said Captain Brendan Deehan.

Wednesday they shared a bit more about the 17-year veteran firefighter who followed his father into the FDNY, was a loving husband, father of three, soccer and baseball coach, law student and  a musician.

"He was promoted to battalion chief with 13 years on the fire department," said Battalion Commander Brian Fink. "That's pretty amazing. I don't know if anybody else has done that in 13 years."

But Chief Fahy's bright star was extinguished Tuesday when flying debris from a house explosion in Kingsbridge struck and killed him.

"It's pretty devastating when you go out the door and expect to come back and one of your brothers doesn't come back that affects everyone," Fink said.

Police got a tip a few weeks ago that the house on W. 234th Street was being used to grow marijuana.

Investigators tell NY1 they are going on the theory this was a natural gas explosion, and they are looking at whether someone tampered with the gas line, perhaps to enhance the plants' growth. Sources also say windows in the house had been sealed shut.

A man who rented an apartment in the home, 34-year old Julio Salcedo, was quickly called a "person of interest" in the investigation. He was arrested in New Jersey after the explosion on an outstanding warrant in an unrelated case.

Investigators returned to the scene Wednesday sifting the debris for clues.

While here and in Yonkers, where Chief Fahy lived, friends and family remembered the fallen firefighter they knew and loved.

"The loss is tremendous for us," said Battalion Chief Mike Woods. "We're going to our best to make sure his memory lives on."