Deadly force to protect property

What if a dog got off of a chain or out of a pen and someone was trying to help you out. knew it was your dog. Lets say he was bringing the dog back and almost got to the pen and realized that he left his phone in his truck and was waiting on a call, so he turns back to go get his phone before he gets to the pen and you blow his head off because all you saw was him walking away from your pens with your dog? Why not just roll up on him and give him a good ole whoopin? Im just saying. Not trying to start no problem but I think its pretty sorry to shoot first and ask questions later. A million things could happen and a dog is never worht anyones life or the chance of you spending the rest of your life in prison, so two families lose someone. Now Im not against lethal force, Im all for it but in a sure way. Just like when your deer or turkey hunting, you got to be sure of what your shooting.