Police are investigating after a man was shot and killed in an incident Saturday night involving a city police officer in Brooklyn.

Police say a narcotics officer on an undercover drug operation was sitting on the stoop of 370 Lafayette Street in Clinton Hill around 8 p.m. Saturday night.

They say that's when 49-year-old Shem Walker came out and told the officer to leave and started attacking him. Police say the two struggled over the officer's gun and it went off twice when Walker tried to grab it.

Walker was hit in the chest once and was pronounced dead at Brooklyn Hospital.

The officer suffered a head injury.

Walker's family and friends are disputing the NYPD's account of what happened, saying he was an U.S. Army vet.

Councilwoman Letitia James, speaking on behalf of the family, says while the corner is known for drug activity, Walker was trying to clean it up.

"This gentleman was not involved in any drug activity at all," said James. "In fact, he used to tell individuals who would sit on his stoop to leave his stoop and they would obey. The fact that a undercover officer did not leave his stoop, his property and the fact that there was an altercation, at a time when the family was sitting by the window and didn't hear anyone shout police, raises some serious questions in my mind and in the mind of my constituents."

James says the family is asking for an independent investigation and for the officer to be placed on desk duty.

Police say the officer has been with the force since 2002 and has been working undercover for the past 26 months.