Protesters in New York have demanded accountability after police fired at a suspected fare-evader in a busy subway station, hitting a bystander in the head.

The man, Gregory Delpeche, remains in the hospital in critical condition and has undergone cranial surgery, according to US media.

Police said two officers shot at the suspected fare-evader on Sunday after he refused to comply with orders, muttered threats and drew a knife.

A second bystander, another officer and the suspect also were injured.

New York authorities have made reducing crime on the subway and buses a top priority following a series of violent attacks, robberies and murders. A crackdown on fare evasion is part of that push.

But critics have questioned how the pursuit of a minor offender escalated into the use of lethal force in a crowded space.

Jennvine Wong, of the Legal Aid Society Cop Accountability Project, told The New York Times that police had endangered lives after choosing “in an enclosed space … to use disproportionate force”.

At a Tuesday protest that began outside the Sutter Avenue L Station in Brooklyn, where the shooting incident occurred, police made 18 arrests as community members spoke out and gave out swipes for subway rides.

“Two dollars and 90 cents is not [worth] a bullet shot to the head,” one protester told CBS News, the BBC’s US partner.

Mr Delpeche, 49, was in a different car from the suspected fare-evader, on the way to the job he has held at a local hospital for more than 20 years.

Relatives told US media the wound to his head has left him with possible brain damage. He is sedated and breathing through a tube after undergoing surgery to reduce brain swelling, they added.

Tom Donlon, the city’s interim police commissioner, has ordered a full investigation.

But he told reporters: “Make no mistake, the events that occurred… were the results of an armed perpetrator”.

New York Mayor Eric Adams, a former officer, also defended the officers’ response.

“He was not shot for fare evasion. He was shot because he had a knife and he went after the police officers,” he said on Tuesday.

“I thought those officers responded accordingly.”

The officers involved have not been named but have reportedly been assigned to desk duty pending an investigation.

In a press conference, NYPD Chief of Department Jeffrey Maddrey said that two officers had seen a man – later identified as Derrell Mickles – go through barriers without paying.

Mr Maddrey said body camera footage showed the suspect threatening to “kill” the officers if they followed him, before confronting them with a knife.

The footage shows a train pull into the station as the confrontation escalates. The officers fired Tasers at the man – to no effect – as he attempted to board the train, before he jumped back to the platform.

“At one point, he is advancing on one of the officers with his knife,” Mr Maddrey said. “The officer stands back, he draws his weapon, and both officers at this point fire.”

Two bystanders, a police officer and the suspect were hit.

Mr Maddrey said that the officer realised he had been shot in the armpit but continued to perform “life-saving measures” on the suspect. Both officers then realised that two bystanders had also been hit by gunfire. Two other officers then arrived and aided the wounded.

Officials said that the suspect had a record of 20 previous arrests and a significant history of mental illness.

Janno Liever, the chief executive of the Metropolitan Transportation Authority, said that the incident “started because somebody wanted to come to the transit system with a weapon, somebody who… had a history of crime and a history of violence and even gun charges”.

The police said on Sunday that a knife had been recovered and posted a picture on social media. The next day, however, it posted another message saying the knife had been taken from the crime scene by an unidentified man.

Officers recovered a different knife from the scene, thinking it was the one that the suspect had been carrying, according to the Gothamist.

An NYPD spokesman told the news website that the knife they picked up must have been left behind by another subway rider.

City authorities have attempted to expand the police presence on its transport system following a surge in crime. All stations on the city’s system have security cameras and pilot schemes are being run to scan passengers for weapons.

The MTA last year announced a crackdown on fare evasion, backed by enforcement by police. Officials say that aggressive enforcement can help in catching criminals and removing weapons from New York’s trains.

But the problem continues to grow, with NYPD statistics showing 2,227 arrests and more than 30,000 summonses in the second quarter of this year – around double that of the same period five years ago.