Mott, I personally love all of the legalese and such, but to quote them to the gun haters is pointless IMO. They don't care what the Law IS, they care what the Laws Should Be (in their opinion).

BTW, I thought I read that the Tax Fee to own a Full Auto was around $365 now ?
And talk about requirements for that License, you have to be "squeeky clean."  

I believe the Key to the mystery of this shooter's motive is Did he have the license? Did he legally purchase the rifle that was used? Was only One gun used out of the many he had with him? If he did Not legally buy the gun where did he get it?  I think knowing the answers to these and other questions could lead to  
some unexpected answers.