The truth of the matter is that the only answer for a bad guy with a gun is a good guy with a gun.
furthermore, laws are only for good guys, because bad guys obviously do not obey laws.
If the penalty for murder is not sufficient in convincing them not to murder, then no further law will have any effect at all.
Peace through strength.
That is all.
Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers,