Having a gun does not create, nor does having people armed around the commission of a crime make those individuals supermen or crime fighters. Look in Massachusetts alone, where a CCW holder responding to such a crime stops for a moment and second guesses just how much trouble he will get into, what the civil suit will be like, what the DA will think, does he have another gun for backup while that gun is confiscated as evidence, does he have to worry about repercussions for his family, does he have a leal magazine in the firearm.....
Guns aren't a magical band-aid, and as arms owners we do ourselves a disservice pretending its a magic band-aid for the evils of the world that occur on a daily basis.
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This does look like some kind of lovers spat, seems to be a lot of rage there to do this. Hope she rests in peace, no one deserves that.