A New York City police officer turned himself in to colleagues on the street yesterday and said he might have shot and killed another driver in a predawn road-rage encounter in Upper Manhattan on Sunday, the authorities said.

The officer, Sean Sawyer, 34, approached a police radio car around 1 a.m. near Central Park, said he had chest pains and requested an ambulance. He then told the sergeant and an officer in the radio car that he believed he had been involved in a shooting while he was off-duty in East Harlem about 19 hours earlier in which a man was killed, the authorities said.

The road-rage shooting was similar to many such confrontations: The mundane discourtesy of jockeying for position while trying to exit off a busy highway led to an angry exchange of words from car window to car window. It was after 5 a.m., and the victim and his two passengers had been drinking, the police said.

But this argument, which started on the Franklin D. Roosevelt Drive, did not end with shouts. Instead, it appears that the two drivers took turns chasing each other for several blocks after they exited in East Harlem, the police said.