As Aaron Cockman sat down to watch the new Avengers movie with his four kids earlier this month, the West Australian father had no idea it would be the last time he would see them alive.

Now, the bereaved dad is in the process of planning the funeral for Taye, 13, Rylan, 12, Ayre, 10 and Kayden, 8, after they were murdered in their rural home in Osmington.

Peter Miles, the grandfather of Cockman's children is suspected of murdering the four children before killing his daughter Katrina and wife Cynda, and then turning the gun on himself.

Katrina Miles and her children from Margaret River in West Australia. Photo / Facebook
Katrina Miles and her children from Margaret River in West Australia. Photo / Facebook

In a press conference on Sunday afternoon, 48 hours after Cockman was delivered the horrific news, the Margaret River man faced the media.

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Cockman had been embroiled in a bitter custody dispute with his former partner Katrina but was occasionally allowed supervised visits with their children.

"I have had so much anger ever since I was cut off from my kids, so much anger. That was due to Peter and Cynda making sure I was cut off from my kids. They weren't schooled, they were homeschooled so I never knew where they were or how they were going," he said.

"I would just drive around town hoping to see them somewhere. And I would every now and then and that would get me a few more weeks. It kept me going. [I had] supervised visits and it was amazing. They were beautiful kids," he said.

The last time Cockman saw his kids, they decided to see a movie, a memory that was clearly playing in his mind as he recounted the day to reporters.

"The last movie we watched together … Avengers, the kids loved it. It is not a good time watching a movie with kids. I get to be with them and see their reactions but it is not talking conversations to them," he told reporters on Sunday.

"Because Rylan was sitting down for two-and-a-half hours, we had to go to the park so he could get up and walk around for a bit. Kat has got disabled [parking] so she can park very close all the time and doesn't have to walk too far.

"Rylan and Kat walk off while the two kids are on the little roundabout swing in Busselton, that's the last time I saw them, we had a good time, a great time.

"I saw Taye walking along and she asked for money for shoes. Kat said she used all the little bit of money they had in their wallets.

"I said 'look' and gave them all $10 each and gave Taye $20 and said, 'Keep this in your wallet.' I know they never spend it but it is just them knowing they had $10 in their wallet.

"I think Kayden had $10 in his wallet for months. It's just knowing they had their own little bag, wallet there," he added.

Cockman is now in the process of making plans to lay them to rest.

He spoke with the Shire of Augusta-Margaret River on Monday to discuss their funeral, which is expected to be large and well attended.

Police removed the bodies from the property, Forever Dreaming Farm, at the weekend.

It is expected the funeral will be up to two weeks away as the investigation continues.

Aaron Cockman (inset) is planning the funeral of his children, seen here in at a family wedding.
Aaron Cockman (inset) is planning the funeral of his children, seen here in at a family wedding.

Locals are increasingly turning up to Margaret River community centre and taking advantage of special counselling services.

Extra psychology support services are also being offered to shocked students and teachers at local schools.

"I think it's important to acknowledge it has happened," Western Australia Department of Education school psychology service manager Chris Gostelow said yesterday.

"Also you need to reassure kids that this is an extremely rare event — it's not the sort of event that happens all the time, thankfully, and that they are safe.

"They're safe at school and they're safe at home."

Cockman spoke publicly for the first time on Sunday, telling reporters he believed Miles had been planning the shooting for some time and saw it as a way to fix his problems.

He suggested the Miles family, specifically Peter, were struggling to cope with the news that one of his children, Neil, was extremely sick.

It's understood Neil is waiting for a kidney transplant and has severe "kidney problems".

Katrina and Neil lost another of their brothers around 10 years ago when it's believed he took his own life.

"I thought if something happens to Neil, Kat will not survive this one, she will not be able to lose another brother ... I didn't think about Cynda and Peter. There's no way possible he [could] lose another son."

Cockman suggested his children's grandfather "knew what he was doing" when he killed six of his family members.

"Peter has been trying to hold it together for a long time. I thought, 'There's no way possible he could lose another son, he'll kill himself.'

"I thought, 'No he won't do that either because he's so close to my kids that he would not leave the kids upset for the rest of their lives about it.'

"But he thought, 'I can't live anymore, so this is it for me. But I need to take out everyone because that will fix the whole problem' and he's fixed the whole problem," Cockman said.