Samurai,
Thing 1: It's not "robbery" if you're only securing weapons. If a guy attacks you, and you take his weapon away, that's not "robbery." Now, if you check his pockets for loose change, then THAT'S robbery.
I have no problem with securing the weapon(s) that would have been used against me. Or simply moving them out of reach of the downed suspects until PD arrival.
Thing 2: It's not "fleeing the scene" if you're running from the fear of imminent death or severe bodily injury. It's called "retreat to the wall," and in many jurisdictions, you're only allowed to use deadly force up to the point of clearing your way to run from the situation. Plus, it's good evidence of actual fear. The DA will ask, "If you were so afraid, why did you stick around and wait for the cops to show up? You shot them all; they weren't going to follow you. So why didn't you run away, if you were so afraid?"
You can't have this both ways. Either you are in fear for your life
because the BGs have the opportunity to hurt you (they're still vertical) OR all three BG's are down and incapacitated so they no longer pose a threat.
The DA will ask, "If you were so afraid, why did you stick around and wait for the cops to show up? You shot them all; they weren't going to follow you. So why didn't you run away, if you were so afraid?"
This makes absolutely NO sense at all. When 3 men approach with bats and stated intent and you shoot them all, there is no longer a reason to flee the scene. In fact, if you did, the DA would be
more likely to ask you why you fled when there was no longer a danger from them.
From your post it seems as if you would take any weapons they may have had (knives, guns, bats) and fled with them. This is called tampering with evidence and fleeing the scene. All you've done is to make life difficult for your attorney and your defense much more expensive.
As a counter point, in the immediate aftermath of this case, I'd kick the bats away from each suspect's reach and then tell the clerk to secure the doors until the PD arrived. Next step would be to have clerk notify 911 (if not already done) and request ambulances and PD. This secures the scene and prevents 3rd parties from destroying/altering evidence, keeps unseen BGs outside and will probably make the investigation much neater. While waiting, I might ask the clerk if there is a video survelliance system and if so, don't touch it until the PD arrives.