The "unprovoked" attack occurred about 7 p.m. EDT (2300 GMT) at the 125th Street station in front of a northbound 4 train, and emergency medical technicians pronounced the victim dead a few minutes later, a police spokesperson said.
The identity of the victim remained unknown and the investigation was ongoing, the spokesperson said. The police provided no further information about the suspect.
The incident occurred amid an increased law enforcement presence in the subway system after a few high-profile assaults, even though overall crime is down.
New York Governor Kathy Hochul said three weeks ago she would deploy 750 soldiers from the state's National Guard to help New York City police check commuters' bags in the busiest stations.
Another 250 officers from the New York State Police and the state-controlled Metropolitan Transportation Authority Police also joined the effort, which Hochul said was intended to deter crime.
Crimes on the subway were down about 15% in February compared with the same month in 2023, according to police data. Hochul, a Democrat, said commuters were not reassured by "rattling off" crime statistics.
New York Mayor Eric Adams, who once patrolled the subway when he was a police officer, said he sent about 1,000 additional city officers into the subway in February after a January uptick in assaults and thefts.
He has emphasized that crime remains low on one of the world's largest commuter train networks, with about six felony crimes a day, mostly thefts, on a service that sees more than 4 million daily trips.
(Reporting by Daniel Trotta in Carlsbad, California. Editing by Gerry Doyle)
