A bystander was stabbed Saturday morning during a robbery on the subway, police said.
The robber tried to steal from a 28-year-old man on the southbound C train on the Upper West Side, the NYPD said.
The 28-year-old fought back and the robber instead stabbed a 61-year-old bystander, police said.
The older man alerted the conductor, who called police.
When the train stopped at Columbus Circle, officers arrested the 39-year-old attacker, who police later identified as Jamel Purnell. He faces charges of robbery, assault, criminal possession of a weapon and menacing.
The man who was stabbed was taken to St. Luke's Roosevelt Hospital in serious condition, the FDNY said.
The man who fought off the robber wasn't injured.