South West Superintendent Mick Sutherland said on Friday that police will be investigating the property as a crime scene for up to five days, according to the Times.
Two guns were found with the bodies and police have made no mention of any suspect in the case, suggesting a murder-suicide although this was not confirmed.
He and Katrina apparently had been involved in an acrimonious split, leading Katrina to move in with her parents with her children. A friend of the family, who is in the same home-schooling network, said the children were on the Autism spectrum.
On the farm's website, Cynda Miles said the farm, which they reportedly bought in 2014, was their "forever farm".
The bodies of four children and three adults were found at or near a property in Osmington near the southwestern tip of Australia, Western Australia's Commissioner of Police Chris Dawson told a news conference on May 11.
"When Australia had a mass killing-I think it was in Tasmania-about 25 years ago, it was just so shocking the entire country said, 'Well, we're going to completely change our gun laws, ' and they did", he told comedian Marc Maron during a podcast taping.
"We are devastated by this shocking event".
Terror struck a rural property near Margaret River in Western Australia.
"Our thoughts are with her family at this time as they grieve the loss of a lovely mother and her precious babies".
"At 5.15am yesterday morning, police received a triple 0 emergency call from a male person", Commissioner Dawson said.
The worst mass shooting in recent USA history was the Las Vegas shooting in October, where a gunman killed almost 60 people and injured more than 500.
The body of one adult was found outside a house and the others were found inside.
Another Margaret River Local, Phil Armstrong, said everyone in town knew of Cynda Miles and her family because she was so active in the community.
Detectives from the Homicide Squad and Forensic Crime Scene Unit reached the scene as part of the investigation and the area has been blocked off.
He added: 'The loss of any life is tragic, but four children and three adults, this is a significant tragedy'.
"My reaction is one of absolute disbelief - a whole family gone like that", said neighbour Felicity Haynes.
The killing is the worst mass shooting in Australia since the Port Arthur massacre in 1996, in which 35 people were killed and another 23 seriously injured by gunman Martin Bryant. It is such a small community and it will have such a huge effect.