Based on some of the CCLs I have seen out and about at the range, I am going to say very few are "properly trained".
I am by no means anti-gun. but there are a lot of idiots carrying them.
+1
Not to mention the fact that people who 'are' properly trained don't always hit what they are aiming at during moments of high stress. Imagine how many people were running in front of/away from the shooter. Plus, i'd be worried that one of the 'not properly trained' ccl holders would get tunnel vision and see my gun and decide i was the shooter.
I think it's as dumb to say more guns would have solved this problem as it is dumb to say that limiting him to a low-round count mag. Both 'solutions' assume a lot about the situation and neither are provable.