A Pitt Bull just saved the life of a deaf boy and was known as a gentle house pet. Dogs are generally what you make of them, but beware when they run loose in packs. Same goes for humans.
The Chihuahua is Notorious for attacking humans,like swarms of killer Bees.
Poodles also.
I notice that the man attacked had his dog with him. Pitts are notorious for attacking other dogs.
As you say, when dogs are on the loose, and there is more than one of them, pack mentality takes over.
Pill Bulls can be very gently and good dogs, but they take a strong disciplined owner and should never be allowed to run loose or be alone with any child.
Unlike golden retrievers and black labs, pit bulls were bred for fighting and killing.