Sudden aggression and violence are classic signs of Rabies. I think the key points are 1. Why was the dog not vaccinated?(I forget what age the 1st rabies vaccine is given; maybe it's after 6 months of age?) and 2. How did the dog get rabies (was it loose and caught it from a wild animal? did it get bit by a rabid bat inside the house?).
I believe that generally a dog will behave based on how it was trained. I've seen Rottweilers that were big "pussycats", and chihuahauas (sp?) that would rip your face off if they were only large enough to do so. We don't know whether this Pit Bull was trained to be vicious, we only know that it was behaving consistent with the symptoms of rabies.
Everyone has different likes and dislikes with certain breeds; myself-I'll stick with my Springer Spaniels.