Everything turned out all right, can't argue with the results.
In retrospect, I would be very hesitant to inject myself and my firearm into a deadly force encounter that didn't involve someone I love, or know, and am absolutely sure is an innocent victim.
The turning point I see is the security officer being assaulted with a deadly weapon. She is private security for the complex or does she work somewhere else? Is she in uniform and armed? Did she have the option to not become involved?
All these are factors I would weigh before I made someone else's problem, my problem. Do I want to shoot and possibly kill someone when I don't have all the facts AND a vested interest in the outcome? Do I want to inadvertently subject myself to negative media attention, possible physical and emotional trauma, jail, prosecution and prison? Usually, no.