Nisean Graves, whom area residents describe as homeless, was taken into custody at gunpoint by both NYPD officers and MTA police following the incident.
It happened around 8 a.m. Friday at West 30th Street and 7th Avenue.
Witnesses say the incident started as a fistfight between two men in the middle of the intersection.
At one point, police say, Graves pulled out a knife and stabbed the other man.
Police, who were already nearby investigating an incident on 7th Ave. between 29th and 30th, arrived on the scene quickly.
Officers intervened in the altercation and found a 36-year-old man stabbed in the torso.
"When I went to the corner, the guy was already on the floor bleeding," said Eyewitness Angel Aviles. "And the cops were trying to resuscitate him."
The victim was taken to Bellevue Hospital in critical condition. He died a short time later.
His name was being withheld pending notification of family.
Police immediately took Graves into custody, and he was later charged.
Witnesses described Graves as a homeless person who is known in the neighborhood.
They told Eyewitness News that until now he had never shown signs of violence.
However, Graves is listed as a Level 3 sex offender, and served nine years in prison for attempted rape of a 16 year old girl in Mount Vernon.
The 36-year-old man who died was from Brooklyn, Maryland.
He was wanted in Maryland for questioning in connection with a violent murder.
Eyewitness News is tracking crime and safety across New York City and in your neighborhood
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