A man is dead and a woman badly injured after a dog went “nuts” in Melbourne’s north.

The man’s body was found at a Mill Park home about 6.40pm on Wednesday. The woman, believed to be his wife, was in a stable condition in the Royal Melbourne hospital.

The dog remained inside the house for hours afterwards as police fired shots to stop it attacking again and a ranger tried to capture it.

Senior Sergeant Glenn Parker said the dead man’s daughter-in-law gave consent to destroy the animal.

“The dog belongs to the occupant’s son; the dog’s been here for quite some time,” he told reporters at the scene. “He [the dog] will be taken to a veterinarian, and my understanding is that the owner of the dog has actually consented to that dog being put down.

“It’s an older dog, it’s quite familiar with all of the members of the family and my understanding is it’s out of character for the dog.”

Police believe the dog attack commenced inside the house. Parker said it was understood the man’s wife tried to help him move outside to get away from the animal, but it continued the attack.

A neighbour said there had never been trouble with the animal before.

“There was no stopping it. It’s a giant pit bull,” he told the Herald Sun.

Another witness said the dog was “going nuts”.

The dog, believed to be an American Staffordshire Terrier, was reportedly taken away in an animal control van about four hours after the attack and euthanised on Wednesday night.

The dog was not registered with the local City of Whittlesea council and there had been no prior reports to the council about the dog.

“This is a terribly sad situation and we offer our deepest condolences to the family,” the council’s director of partnerships, planning and engagement, Liana Thompson, said.

“The dog was euthanised last night and council will continue to assist Victoria police with their investigation.”

RSPCA Victoria’s Tegan McPherson said there were several causes of dog attacks, but breed wasn’t necessarily one of them.

“Breed alone is not a reliable predictor of aggressive behaviour,” McPherson told ABC Radio. “From what we’re hearing, this dog didn’t necessarily have a background of aggressive behaviour until this incident.”

Triggers for dog attacks could range from environmental factors to pain and fear, she said.

“Without understanding the context of this particular incident, it could be fear related, it could be something else going on in the environment or it could be related to pathological changes in the dog’s brain or related to pain,” she said.