NY subway rider shot with own gun in rush-hour fight

New York City subway commuters fled in terror as an armed rider who had picked a fight with another man was stabbed and shot with his own gun, police say.

The 36-year-old man is in a critical condition after he was shot in the head on the platform of a busy Brooklyn station on Thursday afternoon.

Police said the 36-year-old pulled a blade and a gun after starting a fight with a 32-year-old man on a train.

The 32-year-old grabbed the older man's gun and fired multiple shots.

Shortly before the gunfire rang out, a woman who was apparently travelling with the 32-year-old appears to stab the 36-year-old in the back during the two men's physical fight, according to viral video captured by another rider.

City officials told a news conference that the older man, a fare evader, had started the fight with the younger man, whom he did not know, on the rush-hour train.

"The 36-year-old male then displayed either a knife or a razor blade, a sharp object, before the two males became engaged in a physical altercation," said an NYPD statement.

"The 36-year-old male then displayed a firearm and during another physical altercation, the 32-year-old male gained possession of the firearm and shot the 36-year-old male."

Officials did not identify either man at the news conference following the incident at the Hoyt-Schermerhorn station.

The 32-year-old was detained by police, but on Friday afternoon the Brooklyn District Attorney's Office cited "evidence of self defence" as the reason no charges have been filed.

The other man was taken to hospital for surgery.

Metropolitan Transit Authority chairman Janno Lieber called the incident "absolutely outrageous".

"The victim here, as the chief said, appears to be the aggressor - but the real victims are the ones I saw on those videos who were going through a harrowing time because they were on the train with someone with a gun," he added. "They're afraid for their lives."

Video posted on social media shows the older man repeatedly shouting "I'll beat you up" at the younger man, and their section of the subway train clearing of riders as the two begin to circle each other.

A woman lunges at the 36-year-old when he pins the younger man down on a seat during a struggle. She is still being sought by police.

"You stab me?" the 36-year-old shouts as blood begins to seep on his back.

Shots are heard as the subway arrives at the Hoyt-Schermerhorn station and panicking commuters in the car sprint for the exits.

Video from other subway cars shows people in tears as they huddle on the ground in the shooting's aftermath. No other injuries were reported.

Earlier this month, New York Governor Kathy Hochul deployed 1,000 members of the National Guard and state police to protect subway riders following a string of headline-grabbing violent assaults.

There have been eight shooting victims in the city's transit system so far this year.