Around 4:20 p.m. this past Friday, the 31-year-old victim and the suspect got into a quarrel on the northbound platform at the station, at 145th Street and Broadway, police said.
The suspect punched the victim in the face and stabbed him three times in the back with an unidentified sharp object, police said to source.
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The suspect came up to the street and ran off, police told source.
The victim was taken to NYC Health + Hospitals/Harlem and was reported in serious condition following the stabbing, police said.
The suspect was described as a black male about 30 years old, standing about 6 feet 2 inches tall and weighing about 180 pounds, with a dark complexion. He was last seen wearing a blue jacket, blue shoes, and a green book bag.
Anyone with information was asked to call the NYPD Crime Stoppers at (800) 577-TIPS or (888) 57-PISTA for Spanish, log onto the Crime Stoppers website, or text tips to 274637 (CRIMES) and enter TIP577.