During the melee, one of the women who had tried to help fell and injured an ankle and an ambulance had to be summoned to help her.
Police were called, as well as Masterton District Council rangers. Mr Bain said 1-year-old Zack - a "lovely, friendly dog" suffered throat injuries and had to be rushed to a vet. His treatment cost $240. He is now recovering.
Mr Bain said Zack had been on a leash while being walked. He said the attack dog had no collar and was roaming free inside the property.
He had been left wondering what could have been.
"What if that dog had decided to attack a young mother with a child in a stroller, what's to say it wouldn't have happened? I wonder what you have to do to keep safe. Carry mace or something?"
The owner of the attack dog was quickly identified and Masterton District Council rangers rounded up the pit bull, seizing it. It will be destroyed.
Council spokesman Sam Rossiter-Stead said dog attacks in Masterton were not becoming more frequent. Attacks on people will likely be fewer this financial year, ending June 30, than any of the last five years.