Genie
it depends on the state, some states it is indeed easier to get a license but even in those states you better not have any convictions of any type. Likewise all require an FBI background check and mental health record it is unlikely but not impossible that a crazy can get a license. It has happened but more rare i think.

The class of weapon would not make a difference, a crazy would just bring multiple wheel guns with him or her instead. If all guns were banned he or she would just cook up a home made pipe bomb .. can't stop crazies no matter what you do, you just have to train yourself to spot them hopefully first. The Secret Service are masters and picking out those with an agenda , they are highly trained as i am also.