A University of Cincinnati police officer was indicted Wednesday on a murder charge in what a prosecutor called “a senseless, asinine shooting” of an unarmed man during a minor traffic stop. Officials say it was the first time such a charge had been leveled against an officer in the county.

The Hamilton County prosecuting attorney, Joseph T. Deters, released a graphic and much anticipated video of the shooting of Samuel Dubose taken by the officer’s body camera that he described as crucial evidence that Mr. Dubose did not act aggressively or pose a threat to Officer Ray Tensing, and that Officer Tensing had lied about being dragged by Mr. Dubose’s car. A grand jury, Mr. Deters announced, indicted the officer on a murder charge, punishable by life in prison, and a voluntary manslaughter charge.

“It was a senseless, asinine shooting,” Mr. Deters said at a news conference, using stark terms to denounce the July 19 killing, the officer’s claims and the officer himself. “This doesn’t happen in the United States, OK?” he said. “This might happen in Afghanistan. People don’t get shot for a traffic stop.”

“This office has probably reviewed 100 police shootings, and this is the first time we’ve thought, ‘This is without question a murder,’ ” he said.