A massive explosion ripped through a house in the Bronx, killing a 17-year veteran of the New York fire department. The explosion sent pieces of the roof flying onto firefighters, striking Battalion Chief Michael Fahy, who leaves behind three young children.

Firefighters were responding to a possible gas leak outside of a two-story residents when the explosion happened at around 7 a.m. on Tuesday, according to reports. About 20 other people were hospitalized, none with injuries that were life-threatening.

Police are still looking into what caused the explosion in the block of brick row houses. Mayor Bill de Blasio said that it was a reminder of the daily risks the firefighters face.

The incident began when a passerby reported smelling a gas leak in the area. An occupant had evacuated before the explosion happened. An hour after firefighters got there, the house exploded. Fahy was on the street outside the home.

Fahy’s father was a decorated battalion chief in the New York Fire Department, and Fahy himself was described as a rising star in the department.

Witnesses said they heard a loud boom and felt the house shake.

Fahy was rushed to the hospital, but it was not enough to save him. The FDNY sent out the following tweet at 11:22 a.m. on Sept. 27: “It is with deep regret that FDNY announces the line of duty death of FDNY Battalion Chief Michael J. Fahy.”

De Blasio announced that flags would be flown at half staff all around the city to honor Fahy’s life.