In the idealistic world of true 2A rights Goetz would not need to worry about being charged with illegally carrying a firearm.
I do, however, have a problem with Goetz's mindset. His statements of intent "If I had had more [bullets], I would have shot them again, and again, and again." seem to indicate a desire for revenge or vengance and one seemingly out of proportion to the incident.
In short, I think the Goetz case is a poor example of self-defense in a legal sense.
With regards to the thugs, "Give me five dollars" is not a request or a plea, but a demand. There's little doubt that a negative answer might very well have resulted in a beating, stabbing or other serious injury. Words are not necessarily worthless, as a previous poster indicated. Had the thug's words been "Could you spare five dollars for me?" the words themselves might have indicated simple panhandling. It could have muddied the waters a bit more for Goetz to establish intent.
As far as the OP's question, it's very likely that in a similar situation, armed with a 5-shooter, the first or closest antagonist will get one round and we then proceed round-robin style until all subjects have been hit. The remaining shot is awarded to the first subject displaying a need for a follow-up shot. Also note that the subjects wounded in the side or back should not be viewed as "fleeing" or showing "proof" that they were disengaging from the conflict. Turning to take cover in such a limited area would result in similar injuries. And it's doubtful that a turn would have been perceived by Goetz as a "retreat" in such CQB in time to hold his fire.
BillCA in CA (Unfortunately)