And on the flip side, why didn't the proverbial, according to the NRA, "Good Guy with a Gun" stop these "bad guys with guns"? Can you cite one example where a gunman involved in a mass shooting was stopped cold in his tracks by a civilian? I'm not talking about trained law enforcers, but your average gun-toting  Joe. I can't think of one single instance of this. Prevention is worth a pound of cure, even in this case, as preventing too easy access to semiautomatic weapons which can be easily and legally modified to perform just like fully automatic ones is a good start. Thus, I don't believe the "Good guy with a gun" myth for one second. 

"But criminals could still easily purchase them on the black market?", you might reason. Wrong again, for if all semiautomatic weapons are banned here in the U.S., their street value would skyrocket and put them out of reach of most criminals--as such weapons if made illegal, would cost as much as an entry-level car, as is the case in Australia.