Forty-seven-year-old Lt. Richard Nappi of Engine 237, a 17-year veteran of the FDNY, was felled by an apparent heart attack Monday after battling a warehouse blaze in Bushwick.

After leading his company into the building to begin fighting the flames, Nappi "became overheated and collapsed," the FDNY said in a statement. Taken to the street by fellow firefighters, he was at first conscious and alert, but went into cardiac arrest after being placed in an ambulance. He died at Woodhull Hospital.

A Bronx native and Suffolk County resident, Nappi leaves a wife and two children.

Nappi was the first FDNY line-of-duty death since August 2009, when Paul Warhola suffered a stroke at a fire scene.

Nationwide, heart attacks are responsible for about half the on-duty deaths suffered by firefighters. The stress, sudden exertion and even noise that are common at fire scenes are cardiac risk factors, but heat is especially dangerous.

The heavy protective gear firefighters wear–which has dramatically reduced burns since being introduced in the 1990s–quickly raises body temperature, especially on a warm day. It was 81 degrees in Brooklyn on Monday.