The Horrific Triple Murder Of Mum, Her Son And Her Daughter

Police are investigating how three members of the same family were killed on Sunday.

19-year-old Teancum Petersen-Crofts appeared in Midland Magistrates Court on Monday after being charged with three counts of murder following the deaths of three people in the north-west of Perth.

Police were called to a convenience store at 1.30am on Sunday. Their investigations lead them to an Ellenbrook home where they found an 8-year-old boy and his 48-year-old mother dead.

Daughter to the woman, a 15-year-old girl, was found critically injured at the scene and later died on the way to Royal Perth Hospital.

Police are yet to confirm the relationship between the 19-year-old man and the three people killed. Police did confirm however, that Petersen-Crofts lived at the house where the three people were found.

Details of what happened at the property are yet to be revealed by police, however officers called it  a "horrific crime".

“A senior homicide detective squad officer said to me that it is potentially the most horrific crime scene that he has ever been called to,” Assistant Commissioner Paul Steel said.

"This is a terrible tragedy for the family involved, for their extended family and for those first responders who were forced to attend ... my heartfelt condolences go out to all of those who have been affected by this tragic incident."

A "complex homicide investigation" is currently underway, with both the house and the convenience store remaining active crime scenes.

Petersen-Crofts has been remanded in custody for one week.