Question about scenarios (commands vs action)

Since I've been reading up and watching on defensive things which I hope never to need (but would rather be educated about ahead of time if I ever do need), I've developed a question.I know this probably varies situationally, but...Let's say these are the hard "givens" (anyone remember high-school geometry 2-column proofs?):0) You're not a LEO.1) There's an active armed robbery, or an active shooter situation.2) Your own life is not being directly threatened, but you cannot escape (or are willing to lay down your life to protect another's).3) Someone else's life is in immediate danger, or they're in immediate risk of grave bodily injury.4) You have a clear shot at the assailant with a clear backdrop, and have verified to your satisfaction and best of your ability that there are no accomplices.5) There is no apparent way to de-escalate without forcing a surrender by means of deploying deadly force (this includes drawing without firing: 'presenting' deadly force).6) Waiting for the authorities to arrive does not seem like it's going to work out for the person(s) in danger.Given the above criterion, do you:a) Take the shot immediately, knowing it's basically an execution with zero warning or chance to surrender,orb) Command them very strongly and clearly to disarm and get on the ground, and cover them until authorities can be summoned?Write-in answers are fine. There may be more options I'm not seeing.This is one of those things I've considered, and it's a blurry area for me. Considerations muddying the waters for me:1) Alerting them may give them time to turn it into a hostage situation, and make make a bad situation even worse.2) Alerting them may startle a jumpy perpetrator, and they may ND into someone, or intentionally open fire first, be it at you or the person upon whom their weapon is trained.Either way, alerting them would seem 50% likely to generate an escalation.And then there's this:3) Shooting them without warning is not something I'm sure even the police would do, short of SWAT snipers. By then, I'm guessing they've tried other options, as well.I know the goal is to preserve life, but I'm not really down with what amounts to executing someone without giving them a chance to give it up and surrender, if there's a viable alternative. Their life deserves respect as well (by my beliefs, anyway), even if they're a complete idiot, ass, and criminal.Bonus question: They're -not- fleeing, and your clean shot with a clean backdrop is from their rear. Do you take that shot?Like I said, I know it's likely to vary by situation, but given the above criterion, what is actually the most likely correct call? Is there any actual guide to that sort of thing?You hope you'll never run into the situation personally, but it's one of those scenarios I've thought of since starting to review personal defence materials, and I'm honestly not sure what the correct answer is. There may be more than one correct answer: Legally vs morally/ethically.I'm sure there will be differing opinions on the matter, but let's please keep it civil. via /r/CCW http://ift.tt/2qUPnnE