There's a solution to pit bulls that does not involve a gun.
They're called Rottweilers. Just let go of the leash and watch them do what they do.
Wanna consistently stop a Pit Bull using another dog? Better think in the neighborhood of a Kurdish Kangal, Anitolian Shepherd, Caucasian Ovcharka etc. Very large flock guardians would be the way to go.
I hate to hear of this incident. I hope the guy and his dog will be o.k. Be careful out there, as this can happen anywhere. I don’t understand not carrying while out walking.