A rookie New York City police officer shot and killed an unarmed 28-year-old man in a darkened stairwell in Brooklyn late Thursday night, according to the police. Police Commissioner William J. Bratton said that the victim, Akai Gurley, was “a total innocent” and called the shooting “an unfortunate accident.” He was not engaged in any activity other than trying to walk down the stairs, Mr. Bratton said. Mayor Bill de Blasio was also quick to offer his condolences to Mr. Gurley’s family. “This is a tragedy,” he said. The officer who shot Mr. Gurley, Peter Liang, has been on the...