A New York police detective shot and killed an unarmed man, whose hands, a witness said, were on the steering wheel of his Honda, after he had been pulled over early Thursday for cutting off two police trucks on the Grand Central Parkway in Queens, the authorities said....The shooting, which occurred at 5:15 a.m., was the latest in a series of episodes in which police officers fatally shot or wounded civilians...A passenger in Mr. Polanco’s car, Diane Deferrari, said in a phone interview Thursday night that just before pulling the car over, officers appeared irate that Mr. Polanco had cut...