The officer used the broken taillight as the justification to confirm or not if the driver was a suspect in some local robberies. The driver fit the description. From that point on it went downhill. I don’t know if it was a legit shoot by the police or if the driver was in the wrong.
According to another FR thread, police radio info was that the vehicle was stopped because the occupant matched the description of an armed robbery suspect; nothing about a taillight.