Now it looks like the most important features of the original narrative were incorrect. First of all, the police officer didn’t stop Castile because of a “busted taillight.” We know that from the police radio recording. At the time, the police were on the lookout for two suspects in the armed robbery of a store in the area, and Castile and Reynolds fit the description. The officer who made the stop reported that he was about to stop the vehicle for that reason.
This fact changes the nature of the incident more than any other. An officer who thinks he may be stopping armed robbers will have a different mindset — about the threat level — from the one he’d have if he were just stopping someone for a broken taillight. He’d be more likely to suspect the presence of a gun, and suspect that it could be used against him. He’d be justified in firing into the car if he had to, even with other people in it, to save his own life.
Meanwhile, a photo posted by a bystander seems to show that the Castile car had two functioning taillights anyway. (Since the video streamed by Reynolds was in daylight, this image would have had to be from later in the day. That would fit, however, with the time it probably would have taken the tweeter, Rashad Turner, to get to the scene.)