It happened early Monday morning, when police say a man believed to be homeless was harassing people on a southbound D train that was pulling into the Rockefeller Plaza station.
Authorities say the 27-year-old victim tried to intervene, but the suspect pulled out a pocket knife and stabbed him in the stomach.
The assailant then fled once the train was at the station.
The victim was taken to New York Presbyterian and is in stable condition, according to police.
"It doesn't make any sense for me to get on the train and I'm assaulted because some whacko wants to hurt me," straphanger Pedro Vega said. "You understand, doesn't make any sense at all."
Witnesses described the suspect as being in his 50s, but so far, police have released no other information.
"I just don't understand why there are no police officers," Vega said. "I don't know what's going on with the government. They need to bring transit right back."
No arrests have been made as police continue to investigate the incident.
The early morning attack comes a week after a train cleaner was brutally beaten when he tried to stop a homeless man from harassing two riders.
And just last Saturday, a 64-year-old man was beaten in the head with a rock on his way home from work.
According to the latest NYPD crime stats, in July there were 342 crimes in the subway, compared to 295 in July of 2021. That's a 14.8% increase.
"It's scary, we need more protection, we are citizens, we pay taxes," straphanger Marina Blyuzer said. "We need more protection, we need more police, we need more train police. We need to find a way to protect the public."
Anyone with information in the latest incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782). All calls will be kept anonymous.
The public can also submit their tips by logging onto the Crime Stoppers website at WWW.NYPDCRIMESTOPPERS.COM, on Twitter @NYPDTips or by texting their tips to 274637 (CRIMES) then entering TIP577.
EXCLUSIVE | Bronx apartment residents say they are being terrorized, beaten by teens who come to building
Apartment residents say they are being terrorized, beaten by teens
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