I carry- and it is NOT in order to exact Gods justice on people in this and other examples. No matter how heinous that's why we have police and courts My ONLY 2 reasons are for my own personal protection should MY life be threatened...or ditto my family- any other situation is none of my business...and I may not really understand that situation anyway. The other reason is that I can, it is a right (and a responsibility). As they say- use it or lose it.
Once you shoot someone, your life changes, I don't want to do that because some asshole cut me off, or I got in a fist fight with a bigger guy, or I misinterpreted a situation that didn't involve me at a mall.