Only because I’m sure that this is headed outside of MPSIMS based on the comment/non-comments already:
Many/most sane citizens are aware that it is in fact possible for an armed person to prevent a crime, save a life, or what have you. However, individual anecdotes are not really relevant in building responsible public policy that works for all citizens. Yes, it’s possible that in an alternate universe where no one was allowed to carry guns that dude with the axe might have killed the clerk, and maybe someone else as well. That doesn’t mean that this is somehow evidence that it is good for American citizens in general for the citizenry to be armed.