Black Lives Matter activists and their allies in Congress are demanding “justice” and “accountability” in increasingly incendiary and racially charged language after the tragic death of a mentally unstable homeless man on the New York City subway this week.

Described in press reports as a Black street entertainer well known to many in the Times Square district, Jordan Neely died from compression of the neck Monday after subway riders subdued him to stop him from screaming at and harassing people on an F train at Manhattan. One of the passengers who subdued him, a White Marine Corps veteran, held him on the ground in a chokehold while two others restrained his flailing arms.

Video of the incident shows Neely losing consciousness at some point during the struggle. Police and paramedics arrived at the scene moments later. He was taken to a Manhattan hospital, where he was pronounced dead.

The 24-year-old Marine, whose name has not been released, was taken into custody and released without charges. The medical examiner’s office classified Neely’s death as a homicide, but the office of the Manhattan district attorney, Alvin Bragg, said the matter is under investigation and Mayor Adams called for deliberation.

“We don’t know exactly what happened here,” Mr. Adams said in an appearance Wednesday night on CNN. “And so, we cannot just blatantly say what a passenger should or should not do in a situation like that, and we should allow the investigation to take its course.”

Activists such as Al Sharpton, though, are demanding that the incident be investigated as a case of manslaughter, and others in his camp were already holding vigils and protests in New York — some of which grew unruly — Wednesday night and Thursday. A New York congresswoman, Alexandria Ocasio-Cortez, called it a “public murder” even before full details of the incident were known.

“Jordan Neely was murdered,” Ms. Ocasio Cortez said on Twitter. “But bc Jordan was houseless and crying for food in a time when the city is raising rents and stripping services to militarize itself while many in power demonize the poor, the murderer gets protected w/ passive headlines + no charges. It’s disgusting.”

A Democratic colleague of hers, Congresswoman Ayanna Pressley of Massachusetts, struck a similar chord. “Black men deserve to grow old — not be lynched on a Subway because they were having a mental health crisis,” she said. “Jordan deserved better. Accountability now.”

Another left-leaning politician, Julia Salazar, a New York state senator, called Neely’s death a “lynching.” New York City’s comptroller, Brad Lander, said, “NYC is not Gotham. We must not become a city where a mentally ill human being can be choked to death by a vigilante without consequence. Or where the killer is justified & cheered.”

The incident comes amid rising tensions over crime and increasing lawlessness on the New York City subway system. After several high-profile incidents involving mentally unstable homeless people — including a shooting incident last year that left 10 people wounded — Mr. Adams promised to beef up police patrols and deploy mental health workers on the subways.

Neely had reportedly been arrested more than 40 times since 2013 on charges including assault, criminal trespass, and transit fraud, and had an active warrant for assault in connection with a 2021 incident. Witnesses told the New York Times that he was acting in a “hostile and erratic manner” before he was subdued, screaming, “I don’t mind going to jail and getting life in prison. I’m ready to die.”

Despite the boost in police presence, crime on the city’s transit system rose by 30 percent in 2022 compared to a year earlier, outpacing a 22 percent citywide surge. The increase is despite ridership levels that are 60 percent below pre-pandemic levels. The city is currently spending an additional $20 million a month on overtime to fund an extra 1,200 cops on the subways on top of the 2,600 already assigned to the system.

Under New York law, people who feel threatened or have a reasonable belief that they need to defend themselves or others may use physical force. Use of deadly force is justified only if the victim believes the assailant is threatening the person’s life.