A pitbull attacked my dog and eight bites and an artery was split - what about a stn gun to stop the fight?

It was a dog we knew, she has attacked four dogs this year. Unprovoked and unstoppable. I read others saying walk the other way, blah blah, but what about when a dog, any breed, is attacking, biting and won't let go. Will a stun gun stop it? The majority of places say use one. What do you think?