The victims of the triple Perth murder have been identified.

A 19-year-old man has been sent to a psychiatric facility after being charged with the murders of an eight-year-old boy, a 15-year-old girl and their mother at a suburban Perth house.

The boy and his 48-year-old mother were found dead inside the Ellenbrook home and the teenage girl was found critically injured in the backyard but died on the way to hospital on Sunday.

Michelle Petersen, 48. Image via Facebook.
Bella, 15, and Rua, 8. Image via Facebook.

Flanked by two security guards, Teancum Vernon Petersen-Crofts appeared in person at Midland Magistrates Court on Monday to face three murder charges.

He looked around the public gallery before sitting down and accusing another person of carrying out the attack.


"A criminal wanted to take me out bush - he did it and he came back for my family," Petersen-Crofts said.

The magistrate told him he didn't need to say anything, but he replied: "I have to 'cos mamma is with me".

After the magistrate said Petersen-Crofts would be sent to a psychiatric facility as there were concerns for his mental health, Petersen-Crofts said: "I was painting a picture of Jesus and stayed there for two months".

"He punched me in the head so hard. I left because I had to. I was that scared he was going to kill me.

"Mamma told me to save myself".

Petesen-Crofts then told a security guard standing by his side that he looked "like a serial killer."

He was remanded to the secure Frankland Centre unit at Graylands Hospital and will face Stirling Gardens Magistrates Court next week.

The accused. Image via Facebook.

Police have confirmed he lived at the Ellenbrook home and it is believed he is related to the victims.

Assistant Commissioner Paul Steel told reporters on Sunday a senior homicide squad investigating officer had said it was "potentially the most horrific crime scene he has ever been called to".

"It is a very complex and I would say horrific crime scene."

Police were initially called about 1.30am to a nearby convenience store before they went to the home.

They continue to comb the crime scene.

A nearby neighbour said the street was usually quiet.

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