First, I think he did a great thing. But...
If he had to go out to the parking lot to retrieve his gun from his vehicle, did he think about calling 911? I'm sure the bank has an alarm, but he could have given a description, etc. Now it worked out that he gave them the whole bad guy, but I would also want the cops to know who I was if I were going back in with the gun.
That's the second time he's had to go to a parking lot to get a gun. Maybe it's time to carry it on his person?
"An armed society is a polite society." Robert A. Heinlein
"After a shooting spree, they always want to take the guns away from the people who didn't do it. I sure as hell wouldn't want to live in a society where the only people allowed guns are the police and the military."
William S. Burroughs