[hga]

The first two rules of gun safety is that there is no such thing as an unloaded gun (a rule of attitude, admittedly), and that you never let the muzzle of a gun cover something you're not willing to destroy. Rule 3 is to not to put your finger on the trigger until you're on the target, which is not violated here, 4 is to be sure of your target and what's behind it, you might not be doing the latter since you're so sure it's unloaded.

From the viewpoint of US law, you have almost certainly committed a serious crime, unless the other party is playing along, and also believes the gun is unloaded (and there has been at least one recent tragic training fatality where the gun indeed turned out to be loaded).