A 20-year-old man was hit Wednesday while riding a northbound J train near the Delancey Street - Essex Street station on the Lower East Side.
It happened during the evening commute home at 5:20 p.m.
The attacker ran off when the train stopped.
Police say the two men had been arguing before the assault. It is not known what their dispute was about.
The victim was taken to Bellevue Hospital where he's expected to survive.
So far, there are no arrests.
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