A New York subway rider was left with a fractured skull after a fellow passenger hit him over the head with a metal pipe.
The New York Police Department (NYPD) said the incident took place on a train in Manhattan after the pair became embroiled in an argument.
As the fight escalated, the man hit the 59-year-old victim in the face with a metal pipe, before leaving the train and fleeing at Chambers Street subway station.
The injured man was taken to a nearby hospital where police said he was in a serious but stable condition.
He is being treated for a fractured skull and a broken eye socket.
Video of the altercation released by the NYPD showed the two men exchanging words with each other and the aggressor gesticulating towards his victim.
He then stands up and strikes the victim as he too begins to rise to his feet.
The injured man is then seen clutching his head, as his attacker collects a trolley had been brought onto the train and prepares to leave.
Police are now trying to identify the suspect, who is thought to be in his twenties and was wearing a black cap and blue t-shirt at the time of the incident.