No future in starting something you can't finish.
Lets say that you were so good and so quick that you actually engaged them and won. How many rounds later? Where did they all go? How many people other than BG's are down?
If ANY one gets hit, it will be a long protracted legal battle that would cost you big bucks when you got sued by the families of those you were trying to protect. If a bystander did by chance get killed, would it have been worth it?
Consider also that the whole incident would be recorded. The decision that took you seconds to act on, would be dissected piece by piece for months and rehashed over and over by experts and jurors.
It could be argued forever that you started the shooting. Like I said, there is absolutely NO future in starting something like this.
Now, if one of them starts shooting ,you do what you must do, but this is a scenario where it is better to react than to act.