There's nothing inherently wrong with a loaded gun, if it's secured. Leaving a loaded gun somewhere where an unsupervised child can get ahold of it is irresponsible, and deserving of swift and severe punishment.
What sort of a cop would not know that? And really - what sort of a cop would not make sure his children understood that a mishandled gun can be dangerous? Even the NRA tells kids to stay away from guns without supervision.

What is the point of rules that are not enforced?