“Mr. Gray suffered a severe and critical neck injury as a result of being handcuffed, shackled by his feet and unrestrained inside the B.P.D. wagon,” she said.

Despite repeated stops to check on Mr. Gray, the van driver, Officer Goodson, and other officers never belted him in, she said, at times leaving him face-down on the van floor with his hands behind him. Though there has been speculation that the police intentionally gave Mr. Gray a “rough ride,” intended to slam him against the metal sides of the van, Ms. Mosby did not refer to that possibility. She charged only Officer Goodson with second-degree murder, the most serious crime facing the six officers; he was also accused of manslaughter, assault and misconduct in office.

Mr. Gray’s condition deteriorated, she said, as officers repeatedly ignored his pleas for medical attention and ignored obvious signs that he was in distress. At one point, she said, when officers tried to check on him, Mr. Gray was unresponsive, yet no action was taken. He died of his injuries a week later.

Lt. Brian Rice was charged with manslaughter, assault, misconduct in office and false imprisonment. Officer William G. Porter and Sgt. Alicia White were charged with manslaughter, assault and misconduct in office. Officers Edward M. Nero and Garrett E. Miller were charged with assault, misconduct in office and false imprisonment.

As Ms. Mosby finished reading her announcement, the news began to ripple through a crowd of African-American residents and activists who had pooled around her. Edward Jenkins, 44, a motivational speaker and musician who goes by the name Voyce, approached and could hardly contain his surprise when he was told of the charges. “Are you serious?” he said.