Depends on the state and even country. Because the basic code for the Castle Doctrine is this...
A Castle Doctrine is a legal doctrine that designates a person's abode or any legally occupied place – e.g., a vehicle or home, as a place in which that person has protections and immunities permitting one, in certain circumstances, to use force to defend oneself against an intruder, free from legal prosecution for the consequences of the force used. The term is most commonly used in the United States, though many other countries invoke comparable principles in their laws.
In Ohio it extents to a vehicle or residence of any you are legally in when someone attacks you or another person in the same. But not a business, but you are allowed to defend someone else or yourself if it appears your/their life is in danger no matter where you are. But the law does require you to retreat if it is possible when you are threatened if you are out in the public.
But for this case of the thread, the shooter was clearly in the wrong. Even here in Ohio he would have been charged.