Good question. As a civilian I've never shot another civilian. I have, however, displayed my firearm three times in the past 14 years* (interestingly, twice in a Home Depot parking lot!) and mentally committed myself to using deadly force if the mope took one more step forward or raised his tire iron. Inasmuch as we have very discerning and rational squints, goblins, cut-purses, four-flushers, and goat-petters in my state, a fourth kind of close encounter was never necessary.
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- It's been 14 years since my state passed a concealed handgun law.