Let's not have a rush to judgment.
The fellow had only ONE handgun, a semi-automatic pistol. He purchased that legally, despite being as deranged as yer average NRA member. He wasn't out to harm innocent folks.
He could has seen an member of al-Qaeda and tried to protect people. We don't know what happened. We do know he was performing his civic duty and carrying a gun and we do know there are evil people out there from whom the rest of us need protection.
Mistakes can happen in the defense of freedom. We need to give this law-abiding, vigilant citizen the benefit of the doubt and commend him for his sacrifice. This country would be a safer place if more people carried guns.