This is the problem with pits. Even when they are properly socialized, they can go off at any moment. And as a law enforcement officer once said, they are built to kill. Their jaws can do tremendous damage in a very short period of time.
Your story makes me decide to be even more cautious about this.
Pittsburgh Steeler Joey Porter has 2 pit bulls. I am sure they were well cared for, but one day they got out and killed the neighbor's miniature horse. What ticks me off is that the dogs were returned to him. Had they been my dogs (or any other Joe Schmo), I would bet they would have been destroyed.
People say that socialization is the key, but if they were honest, I would love to know how many people properly socialize their pit bulls.