The fire broke out on the 12th floor of a condo building on Metropolitan Oval in the Parkchester section around 1:30 a.m. Tuesday.
The flames were put out quickly, but four people suffered injuries. Emergency workers could be seen doing chest compressions on one victim in the back of an ambulance.
A man and woman were both taken to Jacobi Medical Center in critical condition. Authorities later said a 46-year-old woman died at the hospital.
A 45-year-old man and their 14-year-old son remain hospitalized. A fourth person was treated at the scene.
The woman's co-worker said she was a beautiful person, a hard worker and had a great heart.
As smoke poured through the building, multiple families, including children, were briefly evacuated while the smoke dissipated.
Firefighters busted the glass windows to try to let out some of the smoke. Residents said the hallway was full of water and ashes.
Neighbors want to know how the fire started.
"When one apartment is on fire, we're all in danger," said resident Dionne Holmes. "This is serious."
The FDNY said the cause of the fire was accidental from electrical wiring.
The FDNY took a photo of the firefighters who performed the rescues and described their harrowing efforts.
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