Rural WA murders unpredictable: Premier

Aaron Cockman believes his four children were killed by their grandfather on a rural WA farm

The murder-suicide of seven people at a rural property in Western Australia could never have been predicted and the cause may never be known, the state's premier says.

Peter Miles, 61, his 58-year-old wife Cynda, their daughter Katrina, 35, and her four children - daughter Taye, 13, and sons Rylan, 12, Arye, 10, and Kadyn, eight - were found dead at Forever Dreaming Farm in Osmington on Friday.

Three guns licensed to Mr Miles were found at the property in the Margaret River area and the family all suffered gunshot wounds.

"Everyone is shocked and surprised. It's not like anyone had an inkling what was going to happen and, of course, the perpetrator is no longer with us - he can't tell," WA Premier Mark McGowan told 6PR radio on Monday.

"Why he did it, what he did, you can only ever surmise."

Asked if he thought the community would ever know the reasons, Mr McGowan replied, "Probably not."

"As far as I'm aware, there was no evidence that he had any sort of mental health issues that could have resulted in the firearms being removed from him, so it's not one of those situations where you could have predicted what might occur."

Mr McGowan visited Margaret River on Sunday and spent half an hour with Aaron Cockman, the father of the four children and other family members.

"He's obviously a grieving father and he's going through a difficult time," the premier said.

"It's a shocking, unexpected, awful tragedy and lots of people will suffer for years to come out of this."

The premier also met the two police officers first at the scene just after 6am on Friday following an emergency call at 5.15am.

"They did everything by the book ... they went there ready for any sort of danger and they found what is no doubt one of the most confronting scenes anyone could ever find."

Mr McGowan expects a police report for the coroner to be ready within the next couple of months.

"It's pretty clear what's occurred, but whether there's any motives ... they're investigating."

Among the issues likely to be examined by the coroner is the use of guns on farms.

"We have some of the strongest firearm laws in the world ... It's hard to work out what we could do differently," Mr McGowan said.

Mr Cockman on Sunday speculated Mr Miles "thought this through" and shot his daughter and her children, as they lay in their beds.

Mr Cockman had been embroiled in a bitter dispute with Katrina about access to the children, and blamed her parents, saying they "cut me off from my kids".

He said Peter had lost a son years ago and could not bear the thought of losing the other, Neil, who is gravely ill with a kidney illness.

"He's just gone 'right ... I can't live anymore, so this is it for me. But I need to take out everyone with me because that will fix the whole problem'."

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

Suicide Call Back Service 1300 659 467.