After a shooting on a subway in downtown Brooklyn sent New York City commuters fleeing for safety, prosecutors said no charges have been filed against the gunman, citing evidence he was trying to protect himself.

"Yesterday's shooting inside a crowded subway car was shocking and deeply upsetting,’ said Oren Yaniv, spokesman for the Brooklyn District Attorney's Office. “The investigation into this tragic incident is ongoing but, at this stage, evidence of self-defense precludes us from filing any criminal charges against the shooter."

A 36-year-old man was shot multiple times, including in the head, after a man whom he threatened with a gun took it and used it against him, according to the New York City Police Department. The shooting occurred after a confrontation had unfolded between the two men who police have not identified on a busy train during the Thursday evening rush hour.

Videos shared on social media showed the physical confrontation that preceded the shooting, as well as its aftermath as some passengers on the subway huddled and shouted for police while others fled in a panic. One week prior, safety concerns in the subway prompted Gov. Kathy Hochul to send hundreds of National Guard members to patrol and search passengers’ bags for weapons at busy train stations to prevent violent crimes.

At a news conference after the shooting, Metropolitan Transportation Authority Chairman Janno Lieber reinforced the need for such measures with the words, "the subway is no place for guns."

"The real victims are the people I saw on those videos who are having a harrowing time because they're on a train with somebody with a gun," Lieber told reporters at the news conference, video of which the NYPD shared on social media site X. "They're just trying to go about their lives."

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Online video shows older man threatening other man: 'I will beat you up'

The violent confrontation began around 4:45 p.m. when a 32-year-old man boarded a train headed for the Hoyt-Schermerhorn station and was quickly accosted by the 36-year-old, said NYPD Chief of Transit Michael Kemper at the news conference.

The older man was "described by multiple witnesses as being aggressive," Kemper said.

Footage posted to social media shows the 36-year-old man repeatedly threatening the 32-year-old man, saying “I will beat you up" until the younger man stands up and readies himself for a physical confrontation. Fellow passengers implore them to stop, and one woman can be heard saying "there are babies on here" as the men take swings at one another and others move away from them to the other end of the train.

Though the fight is eventually broken up by another male passenger, the confrontation doesn't end. Police said the older man is suspected of first brandishing a knife or some sort of sharp object before pulling a gun from his jacket and approaching the 32-year-old. Footage also showed a woman appear to slash the 36-year-old man in the back with a sharp object as he was attacking the 32-year-old.

The video does not show the shooting itself, but several loud bangs can be heard over the commotion of the passengers as the train rolls into the station and they rush out of the open doors.

ABC News journalist Joyce Philippe was aboard the train when it happened and captured video of the aftermath as dozens of other passengers huddled on the subway train.

"Where's the NYPD? Oh my god!" Philippe can be heard saying.

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Police officers at the Hoyt-Schermerhorn station heard gunshots as the train arrived and responded within moments, Kemper said.

An investigation led police to conclude that the younger man was able to somehow wrestle away the gun from the older man and use it to shoot him multiple times.

The older man who was shot was transported to a nearby hospital for medical treatment and was in critical condition, Kemper said. The younger man was apprehended on the platform but has not been charged with a crime.

Kemper said police do not believe the men knew each other prior to the confrontation.

In a Thursday night post on X, New York City Police Commissioner Edward A. Caban praised officers for their quick response to "a senseless confrontation." 

"While the circumstances surrounding this incident remain under investigation, what is absolutely clear is that the moment the doors to that train car opened at the next station," Caban said, "your NYPD officers were there."

New York mayor had deployed National Guard to search passengers

The shooting comes on the heels of Gov. Hochul's move to ramp up security in the subway system following a series of high-profiles crimes.

Just this month, trains were delayed after a train conductor was slashed in the neck as he put his head out a window to make sure the track was clear. And in February, a shooting that broke out on an elevated train platform in the Bronx left one man dead and five others wounded.

Following those recent incidents, the Democrat governor announced March 6 her decision to deploy 750 members of the National Guard and 250 state troopers and transit officers to help the New York Police Department check bags at subway entrances for guns and other weapons.

As part of a larger plan from the governor's office to crack down on subway crime, the measure is also among a legislative proposal to ban people from trains for three years if they are convicted of assaulting a subway passenger. Cameras were also installed in conductor cabins to protect transit workers.

The plan is an effort to "rid our subways of people who commit crimes and protect all New Yorkers whether you're a commuter or transit worker," Hochul said at a news conference last week.

Contributing: Thao Nguyen

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]