Jane and Jessica Cuzens. Photo: via Facebook

Friends of the 46-year-old West Australian woman, who police believe killed her two daughters before taking her own life, are shocked and say she deserves to be remembered as a loving mother.

Heather Glendinning, 46, was found dead in her Port Denison home with the bodies of her two daughters, Jane Cuzens, 12, and Jessica Cuzens, 10, on Monday night.

A friend of Ms Glendinning, Robyn O'Brien, said she could not believe the mother-of-three could have committed murder-suicide.

"I am absolutely shocked. I just can't believe that," she said. "I have other friends here that I have spoken to this morning and for Heather to kill her children is not what we know of Heather, it's not possibly something she could do."

The crime scene at the new housing estate, 366 kilometres north of Perth, was so gory it was deemed by investigators to be "one of the worst crime scenes that they have encountered".

"It's a horrific scene apparently, so it's not a quiet death, so somebody would have to be deranged but Heather loved her children, they were just such a close-knit family," Ms O'Brien said.

The details of what occurred are still being kept a closely guarded secret until details of an autopsy are carried out but yesterday police revealed that it was most likely a murder-suicide by ruling out the involvement of a third party.

Detective Inspector Dave Bryson said the investigation had been "very complex and very difficult".

"As with all homicide investigations we remain open-minded, we're not tunnel vision and as more evidence comes in we will look at that," he said.

"Having said that on the basis of the evidence that we now have, we don't believe there is another party involved in [the case of] the deceased females."

Ms O'Brien said Ms Glendinning had qualifications as a nurse and would do anything to protect her children, including eldest daughter Grace Anne Cuzens, 13, who escaped any harm and was believed to be staying in Perth.

She said Ms Glendinning had listed working in the health industry in 2009 on her Facebook profile, but in more recent emails had mentioned she was studying ethics and law at university to help her in her court case against her estranged husband, Harley Cuzens.

"Justice and ethical behaviour is what she was fighting for," she said.

She said she was angry that her friend's last memory would be in such horrific contrast.

"It breaks my heart, it just can't be Heather. They were so close, they weren't problem kids and all the other people who knew her down here say the same thing," she said.

"I do feel really, really angry on her behalf and on behalf of the girls. The Heather we knew and the family we knew would never do that."

She said that even though she had heard reports that Ms Glendinning was stressed over the ligation with Mr Cuzens, she denied that would be motive to commit murder.

"What has happened in the last month to cause a level-headed, professional, completely resourceful person to do such a horrific thing? It's inconceivable," she said.

"What on earth happened to happened to make her able to do that? They were a wonderful family. I really did think she was the target.

"... I am just shattered; I still hope it isn't true."

Another friend Lesley Komlos also said she could not believe it.

"No. I just don't," she said before becoming too distressed to talk further.

Inspector Bryson said the investigation was winding down and a report would be made to the State Coroner Alastair Hope.

"At the end of the post-mortems we should have causes of death and then what we will do is submit a report to the coroner he will then decide the outcome of the investigation," he said.

It is understood that the playground that was cordoned off by police for forensic testing was the last place the family played before their gruesome deaths.

Support is available for anyone who may be distressed by calling SANE Helpline 1800 18 7263; Lifeline 131 114; Salvo Crisis Line (02) 8736 3295; beyondblue 1300 22 46 36.