They do not think like humans, nor should they be treated like humans. The first thing one needs to understand it that a dog responds to the tone of your voice, not your just your words. This reaction does not clearly tell the dog that his action was not expectable. Chances are, this dog will snap again. It needs to be made clear to the dog that you did not approve.
Some dogs are more voice sensitive then others.
With others, farther measures need to be taken. An example is with my own two dogs. My Husky mix is very voice sensitive and just a tone of great disapproval would make him cower. The message would have sunk in. On the other hand, my 70 pound English Bulldog would need a smack on the rear and a harsh tone.