A man engulfed in flames leapt from the fourth-floor window of a burning Bronx apartment where firefighters found another man dead Wednesday, horrified witnesses and FDNY officials said.

Ring camera video shared with the Daily News shows firefighters battling heavy yellow and red flames shooting from the burning fourth-floor apartment on Montgomery Ave. near W. 174th St. in Morris Heights at about 7:45 a.m.

FDNY Fire Marshals have yet to determine what sparked the blaze. Neighbors said they saw someone lighting a small fire in the fourth-floor hallway about five hours before the apartment fire broke out.

As the fire raged early Wednesday, witness Uneek Valentin, 46, watched from the window of her fifth-floor apartment as her neighbor made his death-defying jump to escape the flames.

“I heard him screaming. I thought he was on the roof, but then I saw him in his apartment window. He was on fire. He was screaming in agony,” said Valentin, who lives with two of her four kids in a fifth-floor apartment in the building. “He broke the window, and then there was a plume of black smoke.”

“He threw himself out the window.”

That tenant, a 31-year-old man, was taken to Jacobi Hospital in critical but stable condition, cops said.

Officials could not immediately identify the fatal fire victim, who was found dead inside the smoldering apartment. Multiple neighbors said the dead man was the critically injured victim’s uncle. The pair lived in the same apartment.

“(The man who jumped) is still alive, but his uncle was trapped in the fire,” said Valentin. “He was killed.”

Firefighters respond to a fatal fire at 1484 Montgomery Ave. in the Bronx on Wednesday, Sept. 23, 2026. (Gardiner Anderson / New York Daily News)Firefighters respond to a fatal fire on Montgomery Ave. in the Bronx on Wednesday. (Gardiner Anderson / New York Daily News)

Five more civilians and four firefighters were also injured in the fire, according to fire officials.

The fire remained under investigation Wednesday.

“Fire Marshals are investigating all angles, including if the fire is incendiary,” said an FDNY spokeswoman, who confirmed reports that someone was seen lighting a fire hours earlier. “(We) have been on scene interviewing witnesses and collecting video from residents and neighboring buildings.”

The blaze quickly grew to two alarms and spread to an adjacent apartment, two apartments above, and the cockloft between the top floor ceiling and the roof, FDNY officials said.

Wind may have contributed to how quickly the fire spread. In total, 140 firefighters and EMS personnel responded to the scene, officials said.

Displaced residents wait on the sidewalk after a fatal fire at 1484 Montgomery Ave. in the Bronx on Wednesday, Sept. 23, 2026. (Gardiner Anderson / New York Daily News)Displaced residents wait on the sidewalk after a fatal fire on Montgomery Ave. in the Bronx on Wednesday. (Gardiner Anderson / New York Daily News)

“I ran into my kid’s room. When I opened the door to their room, it was filled with black smoke,” said Valentin. “I rushed to get them out. I’ve been burned out of my apartment. Everything has been destroyed. I don’t know what I’m going to do.”

Displaced residents wait on the sidewalk after a fatal fire at 1484 Montgomery Ave. in the Bronx on Wednesday, Sept. 23, 2026. (Gardiner Anderson / New York Daily News)Displaced residents wait on the sidewalk after a fatal fire on Montgomery Ave. in the Bronx on Wednesday. (Gardiner Anderson / New York Daily News)

The Red Cross has helped 65 people left homeless by the fire find temporary housing, officials said.