He reacted to a charging dog. Very different from a barking dog. If you have ever been attacked by a dog you would realize the scaring it leaves (I was attacked on a beach more than 30 years ago as a 10 year old and still remember it vividly). Furthermore he shot downwards at the dog ie towards the ground. Is it excessive force - probably. Is it completely unwarranted - no. Is the owner to blame as well - yes. Should the mans kids be punished? Should there be a sign in the yard - NO