Well, my first response is going to be, "Oh, it's going to be one of those days," muttered under my breath. Then, obviously, since these individuals probably had it really rough as kids, I'd try to reason with them and explain that I felt their pain and realized they just wanted the same things we all do. Huh? Oh, sorry, spent too much time looking at the MMM site. OK, for real:
Scenario 1: You don't say, so I'll assume I've not been spotted. That being the case, I'll very discreetly retreat to office, make the call, arm myself, and stand by to render assistance until the police arrive.
Scenario 2: Same answer, essentially.
Reasoning: I'm an OK shot, but I don't have the level of training/skill necessary to engage multiple targets. If it has, indeed, hit the fan and innocent lives are in jeopardy all bets are off. I couldn't shave in the mornings if I hadn't at least tried to do everything I could.
"...and he that hath no sword, let him sell his garment, and buy one."
"An armed society is a polite society."
"Power corrupts. Absolute power - is kinda cool!"