(CNN) — Manhattan prosecutors are conducting a “rigorous ongoing investigation” into the death of a man seen in video being put in a chokehold by another rider on the New York subway.

Jordan Neely, 30, died Monday due to “compression of neck (chokehold),” a spokesperson for the New York City Office of the Chief Medical Examiner said. The manner of death was ruled a homicide, but that determination is not a ruling on intent or culpability, which is for the criminal justice system to consider, the spokesperson said.

“This is a solemn and serious matter that ended in the tragic loss of Jordan Neely’s life,” Manhattan District Attorney’s Office spokesperson Doug Cohen said in a statement. “As part of our rigorous ongoing investigation, we will review the Medical Examiner’s report, assess all available video and photo footage, identify and interview as many witnesses as possible, and obtain additional medical records.”

Witnesses told police Neely and another man were riding a northbound train Monday when the other man put Neely in a chokehold, causing him to lose consciousness, a law enforcement source said.

Neely had been “acting erratically” before the incident but had not attacked anyone on the train prior to being put in the chokehold, a witness who recorded the encounter told CNN.

Juan Alberto Vazquez said he was riding the subway when he saw a man, later identified as Neely, enter the car just as the doors were closing. The man immediately launched into an aggressive rant about being “fed up and hungry” and “tired of having nothing,” Vazquez said.

The man then took off his coat and threw it on the floor and said he was ready to go to jail and get a life sentence, Vazquez said.

Many passengers became visibly uncomfortable and moved to other parts of the train car, but Vazquez told CNN it didn’t seem like the man was armed or looking to attack anyone.

Another rider then approached Neely from behind and put him in a chokehold, Vazquez said.

Two other passengers approached, with one seemingly trying to mediate, while the other seemed to be helping the man restrain Neely, Vazquez said, adding that he started recording the incident about three or four minutes after the chokehold began.

In the video, Neely and the other man are seen on the floor of a subway car with the man’s arm wrapped around Neely’s neck.

CNN has not been able to independently confirm what happened leading up to the incident and doesn’t know how long Neely was restrained or whether he was armed.

After a while, Vazquez noticed that Neely stopped talking and moving, he said.

NYPD officers responded to a subway station in downtown Manhattan just before 2:30 p.m., and found Neely unconscious. First aid was rendered and he was taken to a nearby hospital and pronounced dead later that afternoon, the law enforcement source and an NYPD spokesperson said.

Vazquez said he gave his video to police after learning Neely had died.

Neely was homeless, according to a source familiar with his case. He had a history of encounters with the NYPD, a law enforcement source told CNN’s John Miller, including 42 arrests on charges including petit larceny, jumping subway turnstiles, theft, and three unprovoked assaults on women in the subway between 2019 and 2021.

The man who put Neely in the chokehold has been identified as a 24-year-old from Queens, a law enforcement source said. The man is a former US Marine, according to law enforcement and military records.

“This investigation is being handled by senior, experienced prosecutors and we will provide an update when there is additional public information to share,” Cohen, the district attorney’s office spokesperson, said. “The Manhattan D.A.’s Office encourages anyone who witnessed or has information about this incident to call 212-335-9040.”

Neely’s death comes more than a year after New York City Mayor Eric Adams launched an initiative to combat crime and address homelessness in the city’s subway system, including a plan to add more behavioral health emergency assistance teams.

When asked about Neely’s case and the issue of vigilantism during an interview on CNN Primetime Wednesday, Adams said, “Each situation is different. … We have so many cases where passengers assist other riders. We don’t know exactly what happened here until the investigation is thorough.”

Adams referenced his time as a transit officer in New York and said he responded to many calls where passengers assisted others.

“We cannot just blanketedly say what a passenger should or should not do in a situation like that,” Adams said.

New York City Council Speaker Adrienne Adams called for accountability in Neely’s death, saying in a statement, “Let’s be clear: any possible mental health challenges that Jordan may have been experiencing were no reason for his life to be taken.”

“My heart and condolences are with his loved ones during this difficult time,” the council speaker said. “His killing at the hands of a fellow passenger and the responses to this violence that took his life have been not only tragic but difficult to absorb.”

(Copyright (c) 2024 CNN. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

Join our Newsletter for the latest news right to your inbox