The owner of a dog has praised her 11-year-old sister as "very brave" after she helped wrestle away the American bulldog which attacked their mother and was later shot by police.

The property where the dog attacked a woman, with police later shooting the animal. ( ABC News: Edith Bevin )

Ashleigh Templar said five-year-old Boris was a "purebred American Johnson bulldog" which was "asleep" on her mother Melinda's lap before turning on her at a property at Colebrook, north of Hobart, on Sunday evening.

"Why he snapped, we don't know. We've been looking into rage syndrome and maybe a brain tumour," Ms Templar said.

Melinda Templar, 40, is still in hospital and was facing several surgical procedures to repair the damage, Ms Templar said.

Ashleigh's 11-year-old sister Emily helped her father Barry Weston, 78, wrestle Boris away from Melinda, something Mr Weston later attributed to "adrenaline".

"[Boris] only got her arms before my dog Izzy stepped in and started attacking Boris. Izzy is a very protective dog and Emily was very brave and helped get Boris off," she said.

"He ripped her muscles and the doctors have to put mum through two to three surgeries to put it all back together."

Ashleigh said Boris, who was staying at the property, had "been around kids, horses, sheep, cats" and "doesn't need to be named a monster".

"He was far from it. He loved kids and all people."

Mr Weston told the ABC he did not know how he and 11-year-old Emily were able to save Melinda Templar from Boris.

"I don't know how we managed it — I've got cancer and it causes almost a fatigue-type thing, but I think it was just the adrenaline," he said.

He said Melinda had later told him she witnessed "something sort of change in him" and, "his eyes turned red" before the attack.

Ashleigh said Boris was buried on Monday.

"We are all very sad for Boris's death and are waiting for mum to get out of surgery," she said.

Boris was "not a monster", owner Ashleigh Templar said. ( Supplied: Ashleigh Templar )

Dog shot after capsicum spray fails

In a statement on Tuesday, Tasmanian Police said they responded to a call for assistance "after a woman received significant injuries after being bitten by a dog at a Colebrook property on Sunday night".

Police said paramedics were unable to provide medical assistance until Boris was "subdued". ( Supplied: Ashleigh Templar )

"A woman was bitten by the family's pitbull (sic) at the Mudwalls Road property about 10:30pm. Ambulance Tasmania paramedics were unable to provide medical assistance to the woman until police subdued the animal," police said.

"Police were required to incapacitate the animal using a firearm after capsicum spray was ineffective.

"The dog was later euthanised by an Animal Management Officer from the local council."

They described Melinda Templar as suffering "significant but non-life-threatening injuries".

The Johnson variant of the mastiff breed originated in the United States following WWII, when John D Johnson started to selectively develop the breed, which is described as "ideal for companionship or protection".

A website for John D Johnson kennels describes the breed as "unlike any other; their sheer strength and courage coupled with their undying loyalty and devotion make them the ultimate breed of dog for the general public and serious canine enthusiast alike".