A 19-year-old man has been charged with the murders of two children and their 48-year-old mother in the Perth suburb of Ellenbrook, police say.

Teancum Vernon Peterson-Crofts, 19, appeared before the Midland magistrates court on Monday after being charged with three counts of murder.

The three victims were found dead in a house in suburban Perth after police were called to a nearby 7-Eleven store in the early hours of Sunday morning.

Petersen-Crofts, who it’s understood is releated to the three victims, was arrested at Ellenbrook, north of Perth. Late on Sunday police charged him with three counts of murder.

The ABC reports the 19-year-old appeared in handcuffs and was flanked by two security guards, before being remanded to Frankland Centre under a hospital order due to his mental health.

The three victims and the 19-year-old all lived at the home, though police have yet to say whether he was related to them.

Assistant commissioner Paul Steel described the discovery of the bodies as a “complex and horrific crime scene”.

“A senior homicide squad investigating officer said to me today it is potentially the most horrific crime scene he has ever been called to,” Steel said.

Steel said it could take days for the scene to be processed.

“This is a terrible tragedy for the family involved, for their extended family and for those first responders who were forced to attend what was a horrific crime scene,” he said. “It’s a crime that I know will send shockwaves throughout the community of Western Australia.

“I can assure the community that WA police are applying all resources that we can to get to the bottom of what’s happened here.”

Officers were called to the scene from a service station near the home. A man who lives in a neighbouring street earlier told the West Australian he was woken by screaming and yelling about 1am.

“It was real loud screaming and yelling, it sounded pretty heavy,” Matthew Schreck said.