NEW YORK -- In a possible case of road rage, an off-duty police officer was killed early Monday when his motorcycle was rear-ended by a suspected drunken driver who was flashing a blue emergency light sometimes used by volunteer firefighters, police said.

 It was unclear if the driver of the sport utility vehicle -- registered in New Jersey -- was a firefighter, police said.

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Police report at about 12:16 a.m. the off-duty officer was riding a motorcycle north on the West Side Highway at West 133rd Street when it collided with an SUV. The officer was transported to St. Luke's Hospital in critical condition and died later.

The accident investigation caused delays on the West Side Highway during the morning commute.

Mayor Michael Bloomberg identified the officer as Eric Concepcion, 36. Concepcion left behind a wife and two young daughters.

Mayor Bloomberg said Concepcion was killed by a drunk driver and called it a "senseless loss."

Police Commissioner Kelly said the SUV driver had an alcohol level of .12 and will be charged with DWI and vehicular homicide.

Kelly said Concepcion joined the force in 2000 and was assigned to the 42nd Precinct.