(CNN) -- A veteran New York firefighter who darted into a burning high-rise building looking for trapped residents has died.
"New York City and the FDNY suffered a terrible and tragic loss when one of our bravest, Lt. Gordon Ambelas, died while trying to save lives," New York City Mayor Bill de Blasio said.
"We have lost a real hero tonight, and our hearts are heavy."
Ambelas was one of more than 100 firefighters who responded to the blaze in Brooklyn late Saturday night, the Fire Department of New York said.
Fellow firefighters found Ambelas' unconscious body inside an apartment, de Blasio said.
Ambelas was taken to Woodhull Hospital and was later pronounced dead. Two other firefighters suffered minor injuries.
The fire, which broke out on the 19th floor of a 21-floor building, was controlled in about one hour. The fire was determined to be accidental. The electrical cord of an air-conditioning unit where the fire started was "pinched between a bed frame and the wall," according to Fire Commissioner Daniel Nigro.
Ambelas, who joined FDNY in 2000, was recently promoted to lieutenant.
"I ask every New Yorker to keep Lt. Ambelas in your prayers, keep his family in your thoughts and prayers," the mayor said. "We are all very fortunate to have the men and women of the FDNY at the ready to risk their own lives so that each and every one of us can be safe."