I really think y'all are overthinking this. Drive away if possible, which wasn't in this case.
Draw and fire until the threat to you is stopped.
Everyone here has had the benefit to see this video until the end, but for the innocent victim in the car who didn't know how it was going to turn out that was an eternity of rage.
One interesting thought. We are so ingrained with following the rules that the unarmed person in the car was unwilling to save their own life to disobey some; forcefully pushing the car in front of them to make room to escape (yeah, I saw the other right-of-way traffic moving left to right) or sideswiping the other vehicles to squeeze between them to escape.