From the legal standpoint, this is in total a very serious offense. It is extortion, it is a threat of personal harm, with a gun.
Because it happened over a dog, I have no doubt the sentencing will be very superficial. It should not be. The dog is the least part of it.
This perp is someone needs to do some hard time. This is what prisons are for: Threats to society.
A random pick of a Freeper (not the trolls) who could implement our laws in the way you outlined would drop crime on our country by 25% before Christmas.