I would have taken away the gun and made the dad sit in a corner.
Of course, given the good folk around where I live, I'd likely need to stand in line to do it. And remove the gun from a part of the gentleman's anatomy, first. :-)
I still couldn't figure out if it was a 'BB gun' (dangerous, certainly), 'Airsoft pistol' (less so, but still something wiser to be careful with around small kids), or a 'toy' (I'd tell the liberal busybody to MYOB).
Between the poor reporting, and all of the hyperventilating, it's hard to get the facts straight. I can only say with certainty that WBill Jr. wouldn't be irresponsible with a BB gun, or that would be the last time he had it. Period.