I'd keep yourself armed and alert. If possible, find cover that still allows you see the suspect. But the moment you hear Law enforcement nearby, ie sirens, I would either place your firearm on the ground, or re-secure it in your holster if it is concealed. Once LE is on scene, raise your hands and comply with all orders. But absolutely, you should not be holding your firearm when LE arrives. Chances are, we have no idea who is the shooter and who isn't.

If possible, and if not being given orders, try and calmly and clearly, tell LE that the suspect is down. Don't run toward LE, just stay where you are and communicate with them. If they ask if you are armed, I would say "yes" I'm a concealed carrier.

Chances are you will be placed in cuffs. That's ok. It's standard. If you're put in cuffs, and you haven't told LE, tell them now that you're a concealed carrier and where your firearm is. They will take it, that's ok. You'll get it back 'eventually'. If they ask what happened, I would tell them if it was a valid self defense situation. Reddiots will tell you to shut up and ask for a lawyer immediately. And a time for that may come, but if it was clear cut self defense situation I would tell them the whole story.