The victim, identified as Timothy Rudolph, was stabbed during a dispute on the southbound platform of the Coney Island Stillwell Avenue subway station that started at around 11:20 p.m.
He got into an argument with an unknown man that escalated to the two rolling on the platform.
The suspect pulled a knife and stabbed the victim in the back and thigh.
Rudolph staggered to a waiting subway train, where he collapsed in a train waiting car.
The suspect may have gotten on the same train car before fleeing to Stillwell Avenue.
Rudolph was rushed to NYU Langone Hospital Brooklyn, where he was pronounced dead just after midnight.
The suspect was described as a bald man in his 30s, wearing a green shirt and aqua shorts. No arrests have been made.
It was the ninth homicide in the transit system so far this year. Five people had been killed at this point last year.
"I don't feel safe at all, to be honest with you. In my opinion, I feel like the crime rate has gone up here.," Patrick Guerin said.
Transit crime is up on Coney Island by 18 percent driven by an 84 percent increase in grand larcenies. Murder in the subway is up by 80 percent.
But overall transit crime is down 6.1%, with most categories showing significant declines. Robberies are down 15.9%, felony assault down 4.8% and grand larceny down 2.8%.
MTA Chairman Janno Lieber insisted the overall trend is what matters.
"We have to look at those numbers in light of what the historical trend is. Overall, the historical trend is down, down, down. And that's what we're going to keep going," Lieber said.
Lieber said onboard cameras and cameras in the stations are helping to solve and deter crime.
Brooklyn resident Chris Greif believes surveillance cameras make a difference.
"I'm not afraid of anything because on the trains I take, have cameras. Since they put the cameras on, I feel safe," Greif said.
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