Days after a police officer was acquitted of all charges in the fatal shooting of Philando Castile, a black motorist in Minnesota, video of the shooting was publicly released on Tuesday for the first time.

Millions of people have seen the immediate aftermath of the shooting because Mr. Castile’s girlfriend, Diamond Reynolds, had livestreamed it on Facebook. But few have seen video of the moments before that, when the shooting actually took place along a suburban street last year.

This video, from a dashboard camera on Officer Jeronimo Yanez’s patrol car, parked right behind Mr. Castile’s car, was played several times this month to jurors during Officer Yanez’s manslaughter trial but had not been shown outside the courtroom.

The video reveals how a mundane conversation about a broken taillight devolved within seconds into gunfire. The newly released footage provides the fullest account yet of an episode that led to a national debate over police conduct toward black people, but it also leaves unanswered critical questions about what happened that day.