Who is Peter Miles, what happened in Osmington and how is the grandfather linked to the murder-suicide shooting?

Granddad Peter Miles, husband of Cynda Miles and father of Katrina Cockman - who were both found dead at the 30 acre farm - has become the focus of the investigation into the mass-shooting in Australia.

A mum and her four autistic children are among seven people shot dead in the worst mass shooting in Australia in 22 years but who is the man being investigated by police?

What happened in Osmington?

What we know so far:

• Seven bodies with gunshots wounds were found on a rural property in Osmington, Western Australian around 5am local time
• Cops were tipped off by a man 'connected' to the occupants who had raised some concerns
• Five bodies were found inside the property, two were found outside, and two guns were left nearby
• Police say they are not looking for anyone else in relation to the incident
• Katrina Miles and her four 'autistic' children aged eight to 13 were named locally as among those killed

• Her parents, Cynda and Peter, owned the property, though the identities of the two other deceased is not yet known
• Friends described Katrina as a devoted mum who worked tirelessly to provide for her four children
• Posts on Facebook and social media by Katrina and a friend both described her ex as "crazy"
• The incident is a suspected murder-suicide, and is the worst mass shooting in Australia for 22 years

The property, near Margaret River, south of Perth, is owned by Cynda and Peter Miles, whose daughter Katrina, has four autistic children believed to be home-schooled.

Neighbour Felicity Haynes said Katrina's parents moved to the region to build the sustainable farm for their daughter and her grandchildren.

It is not yet known who the two other victims are, though Perth Now and ABC both reported them to be Katrina's parents.

Cops have now confirmed three "longarm" firearms that were recovered at the crime scene belonged to Peter Miles.

Who was Peter Miles?

Not much is known, so far, about the 61-year-old.

He bought the 30-acre farm in late 2014 along with his wife Cynda.

Peter had worked as a farmer and teacher and was formerly the manager of the Margaret River High School farm.

Police Commissioner Chris Dawson said Mr Miles was licensed to own the guns and investigators were not looking for any other suspects, but key forensic evidence was still being combed through.

The seventh person found outside was not named by Mr Dawson but after accounting for the two women and the children, the only person remaining among the dead is Peter Miles.

Cops are also investigating a phone call made to police at around 5am on the day of the shooting.

Mr Dawson refused to reveal any further details about the man who tipped police off.

Australia's worst mass shooting

Australia's worst mass shooting happened in April 1996 when Martin Bryant killed 35 people and injured 24.

After inheriting $570,000 from a friend, Martin Bryant used some of the cash to buy two semi-automatic assault rifles.

His spree was brought to an end when he surrendered to cops after fleeing a burning building.