"I thought 'oh my god', there's so much blood. It was the most horrific thing I have ever seen in my life. He (the dog) had her pinned down to the ground. He (the man) smashed and smashed the dog and sort of knocked it out. And it (the dog) came to and it was sitting there and we could see it and it was going to go for him."
As the dog lunged at him, he yelled at it to go inside and then shut the door after it.
The man's partner stood on the other side of the fence watching in horror. She also called police from her mobile phone.
Ms Featonby said the woman lived on her own and had owned the dog for a number of years and it was a shock to see her with serious wounds.
Kelvin Powell, Hamilton City Council's City Safe Manager said the victim was the dog's owner and she had had the animal since he was a pup.
The dog was a mastiff cross, aged 5 years and 11 months and was the only animal registered at the property.
"At this stage our focus is on understanding the facts of the incident and seizing the dog.
"A check of Animal Control records shows the animal was given a 'menacing' classification in 2010, following an incident involving another dog. That 'menacing' classification requires the animal to be de-sexed, muzzled and on a leash in public. There have been no further reports relating to this dog since 2010.
"Council staff are attempting to enter the property to seize the dog. Once the dog is impounded, it will be dealt with under the Dog Control Act.
"Until we've carried out a full investigation, it would be premature to offer any other comment at this time."