The National Rifle Association’s response to the Sandy Hook massacre is crazy. Duelling with a bad guy with a gun rarely takes down the bad guy with a gun. It generally leads to more innocent lives lost ... and among them, the good guy with a gun, (see the fate of the father-in-law in “Fargo”).
In a crime scene where everyone is being shot, the insanity and indecisions of a firefight are more favourable for the bad/now-crazy guy with an automatic weapon. Unless you have clear shots and a good gun, the odds are heavily against you. Seek cover. Assess risks. Act in the interest of yourself and the people you are with.