A man and a woman and their teenage children are dead in what police are treating as a double murder-suicide at an affluent suburban home.

The 50-year-old man, a 49-year-old female and two boys, aged 16 and 14, were found dead at their home in the Perth suburb of Mosman Park on Friday morning.

A cat and two dogs were also found dead at the double-storey home in one of the city’s wealthiest riverfront suburbs after a person who knew the family visited the property and became concerned.

“Although this investigation is in its infancy, police are investigating this matter as a murder-suicide,” homicide detective Jessica Securo said.

There was no weapon used in the incident, and police had no record of family violence matters involving the family, Detective Inspector Securo told reporters.

Both children had experienced “significant health challenges” and the family had previously engaged with care services, she said.

Police at the Perth home

The family’s three pets were also found dead at the home. (Justin Benson-Cooper/AAP PHOTOS)

A cause of death is yet to be revealed, but a note was found at the home.

At least one of the boys attended Christ Church Grammar School, one of Perth’s top private boys’ schools.

Police have cordoned off the scene on Mott Close, where detectives and forensic officers in blue coveralls have been seen coming and going from the high-walled property.

Police at the Perth home

Police have closed the street as they conduct the investigation into the deaths. (Ab/AAP PHOTOS)

Neighbours have been tight-lipped, but a steady stream of onlookers has been spotted driving past the scene on an adjoining road in the normally quiet suburb.

Support is being provided to first responders who arrived to what police described as a confronting scene.

“This is a tragic and devastating incident where a family has lost their lives, and the impact will be felt by the entire community,” Det Insp Securo said.

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