A Minnesota police officer was acquitted of manslaughter Friday in the fatal shooting of Philando Castile, a black motorist who had just informed the officer that he was carrying a gun.

St. Anthony police officer Jeronimo Yanez was also cleared of two lesser charges in the July traffic stop in a St. Paul suburb. The case garnered immediate attention because Castile's girlfriend streamed the aftermath live on Facebook.

Yanez testified that Castile was pulling his gun out of his pocket despite his commands not to do so. Prosecutors questioned whether Yanez ever saw the gun. Castile had a permit...