Under those circumstances, I could indeed have done no better. But a good number of those circumstances were under my direct control. My choice of an elephant gun as my daily carry. My choice of explosive rounds as a defensive load. My choice of carrying a weapon I am not expert in. My choice of using that weapon to defend those kids. It would not be my fault that the hostage had died. It would still be my doing, and thus, my responsibility.
Again, I utterly reject the notion that a person is responsible for the unforeseeable consequences of actions he had every right to take. If you choose to go to 7-11 to get a Slurpee and as a result of having to wait for you to pass, a car full of kids misses a traffic light and happens to be in the path of a drunk driver, you bear *no* responsibility for accident. None whatsoever. I utterly reject "but for" causation as a moral theory. Yes, had you not gone to 7-11, there would have bee no accident. But that is *not* a moral test.
A much more likely situation is that the weapon is loaded with frangible rounds, a much more sensible defensive load. Of course, this still precludes shooting through the hostage, since frangible rounds have been known to break up from hitting much lighter cover. So it behooves you to know how to shoot well enough to shoot around cover. Or not get involved in hostage situations.
You can load your weapon with whatever rounds you like. If you want to load explosive rounds for target practice and that happens to be all you have when a need for defense comes up, so be it. Unless you have chosen to take on some defensive obligation, you have no obligation to be ready for effective defense. The person who chooses to place you in that situation by choosing to use force must take moral responsibility for the world as he finds it.
These are the things you have to think about before you strap on a weapon. It's not just a show-piece. It's not a toy. It's a very powerful tool. You need to know how, and even more importantly, when, to use that tool, and you need to accept - and expect - the consequences of that use.
No. If you want to strap on a gun with explosive rounds, even if that's horrible for self-defense, you have the absolute right to do that. If that means you aren't prepared for optimal self-defense, then so be it. You have no obligation to attune your actions so that you can more effectively defend others. You can do what you want so long as you choose not to use force. And when you do need to pull your gun, the person who forced you to do that rolled the dice by doing so. All anyone has any right to expect from you is that you do your best, and so long as you do, the fallout is all on their tab.