Margaret River shooting: Relatives 'stunned' by killings

Katrina Miles lived on the property with her parents and four children

Relatives of the family at the centre of a suspected murder-suicide in Western Australia say they are "stunned" by what has happened.

The unnamed relatives of the Miles family said they were "still trying to understand how this could happen".

Katrina Miles, her four children, and her parents Peter and Cynda Miles were all found shot dead at their property in Osmington, near Margaret River.

Police confirmed they believe the killer to be among the dead.

Police Commissioner Chris Dawson said they received a phone call from a man at the property alerting them to the shootings early on Friday morning.

"I wish to strongly emphasise that police do not believe any other person is involved in these crimes. Police are not searching for any other suspects," he told reporters.

He said three firearms found on the property belonged to Peter Miles, 61.

Relatives of those involved, in a statement issued through the police, asked "that the community refrain from speculating on the circumstances around this tragic incident".

Commissioner Dawson said the body of a woman was found in the house on the rural property, while the bodies of a woman and four children were found in a nearby converted shed where Ms Miles lived with her children. A seventh person was found dead outside.

Local media report that Katrina Miles was aged 35, and had four children aged between 13 and eight.

The children's father had been notified of the killings and was "understandably grieving", Commissioner Dawson said.

Cynda Miles, 58, and her family were said to have been active members of their tiny rural community of Osmington, which is about 20km from Margaret River, a popular tourist and wine-growing area.

Memorials have been posted on Katrina and Cynda's Facebook profiles.

Cynda Miles was well known in her community

One neighbour, Felicity Haynes, described them as "lovely people".

"They were a very socially-aware family - doing their best to create a safe community - and that is why it is so shocking to think that could be destroyed so quickly," she told the Australian Broadcasting Corp.

Pamela Townshend, president of the Shire of Augusta-Margaret River, told Fairfax Media: "It's sending shockwaves through the whole community - we're all linked in one way or another, every family."

This is Australia's worst mass shooting since a massacre in Port Arthur, Tasmania, claimed the lives of 35 people in 1996.

That incident led to comprehensive reform of the nation's gun laws, which included a ban on automatic and semi-automatic weapons.

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Australia has had one other mass shooting since Port Arthur - the murder-suicide of a family of five in New South Wales in 2014.