When a dog attacks, it's very easy to play the blame game, but it's not always that simple. Any dog can attack when forced into a situation where they feel threatened or scared. But a lot of the times these attacks take place, they follow a pattern.
He is a classic case of owners taking on a dog that was wrong for their lifestyles. They all seemed to think that they were going to be taking on a dog that was lazy. In fact they had a dog that loved to play, run, be exercised and be entertained.