A blaze in a Brooklyn warehouse on Monday took the life of a New York City fire lieutenant who had responded to the terror attack on the World Trade Center on Sept. 11, 2001.

FDNY Lt. Richard Nappi was the first city firefighter to die in the line of duty in three years, Mayor Michael Bloomberg told a news conference.

A second firefighter was hospitalized in stable condition. Four others suffered minor injuries.

Bloomberg said the 47-year-old Nappi overheated and suffered exhaustion before he collapsed trying to put out the fire at a warehouse building in Brooklyn's Bushwick neighborhood.

Fire Commissioner Salvatore Cassano joined the mayor at Woodhull Medical Center where Nappi was pronounced dead just hours earlier.

The commissioner said the fire broke out on the second floor of a sprawling three-story building on Flushing Avenue at about 1 p.m. Monday.

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He said cardboard began smoldering in the facility whose tenants include a private ambulance service and the city's Office of Emergency Management.

The fire is under investigation, but the commissioner said it started in a way that was "nothing out of the ordinary, nothing strange."

At some point, Nappi "felt dizzy and called for help," Cassano said.

Paramedics worked on him while "he experienced a cardiac event that we will be investigating," he said.

More than 100 firefighters responded to the blaze, which was declared under control just before 4 p.m.

Before joining the FDNY 17 years ago, Nappi served as a state parole officer and a caseworker for Suffolk County, on Long Island.

A resident of Farmingdale, Long Island, he leaves a wife and two children, a 12-year-old daughter and an 11-year-old son.

The fire commissioner called the lieutenant "an extraordinary firefighter and a leader the people would follow."

Cassano said Nappi was also a deputy chief instructor at the Suffolk County Fire Academy in Yaphank, "teaching thousands of firefighters how to stay safe and how to extinguish fires; he was dedicated, he was brave, he was committed to the fire service."

On the day of the 2001 attacks, Nappi was assigned to Engine 7 in lower Manhattan.

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"He responded with valor to the World Trade Center attacks," said Bloomberg. "He helped save and rebuild the city."

The last FDNY member to die on duty suffered a stroke in August 2009, while looking for a working hydrant at a fire in Williamsburg, Brooklyn. The last fatality before that was in January 2008, when a fire lieutenant died battling a fire in Brooklyn's Crown Heights.