I carry to preserve life, liberty, and the pursuit of happiness. Because I'm not a criminal, wanna-be superhero, vigilante, or anything else. As to using "deadly force", I'll make it the very last option in the midst of confrontation, only if that confrontation leaves one of two choices.
I'd ask the Pastor, or council of the church. I see nothing wrong with it, as even that church in Colorado had armed security who put a stop to the madness of an out of control person.
I think OC'ing would have been the best deterrent. I hope more people realize in situations like this are more common place than they used to be. Take notice.