I’ve seen security kick plenty of people out of bars. They sometimes come back wanting to start something with security. In this case, one shot at security from outside who returned fire and apprehended one of them and held him at gunpoint for authorities. A police officer who showed up killed the security guard.

When I was an “emergency coordinator”, we once had a session about what to do during an active shooter situation. Guns were not allowed then. (Unclear now.) It was the Hide, Run, Fight philosophy which was hole up in a secure room if you can, get out if you can, fight back as only a last resort. The trainer’s point was when a police officer shows up, if you are armed, then you might get shot because they will not know who is a good vs bad. They see a weapon and might shoot before they know.