If you take the emotions and hate out of this, just taking the facts of the story, this idiot would never have been able to carry out his killing spree had he not been able to legally buy military weapons and get training on their use at the gun shop.
When you get past all the crap, the basic facts are there to see, as is much of the solution.
That's not true. He could have accomplished the same thing with his pistol. The FACT is that this "idiot" would never have been able to carry out his killing spree had everyone else (but one) not been unarmed and able to defend themselves. The one armed person was a policeman who apparently was outside (He could not be everywhere) and was outgunned. If there had been others who could have defended themselves, the outcome might have been much different. The blood of those victims is on the hands of those who believed that they had no right to be armed to defend themselves.