WA Police are investigating a suspected murder-suicide in suburban Perth after finding the bodies of two teenage boys and their parents in a home in Mosman Park.

A person known to the family attended the Mott Close home on Friday morning and alerted police, according to Detective Acting Inspector Jessica Securo.

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“Police entered the house and located four persons deceased, and three pets deceased,” she said.

“The deceased include two adults, a 50-year-old male, a 49-year-old female, and two boys aged 14 and 16.

“It is believed these persons are known to each other and are part of the family unit.”

Detective Acting Inspector Securo described the incident as a “devastating tragedy”.

Police say all four bodies were located within the property, and that no weapon was used during the incident.

“The family have no reported family violence matters with police,” Detective Acting Inspector Securo said.

Police officers and vehicles on McCabe Street in Mosman Park.

Dozens of police officers are at the scene. (ABC News: Keane Bourke)

“We do know that both children experienced significant health challenges.”

Note found

Police said the person who called police after visiting the house on Friday morning had a pre-arranged appointment.

A long shot of police outside a suburban property

Police in blue forensics suits and detectives have been seen coming and going from the property.  (ABC News: Keane Bourke)

“They arrived to the house and didn’t receive a response,” Detective Acting Inspector Securo said.

“I’m not able to disclose how these persons are deceased, however … there doesn’t appear to be a violent incident that has occurred,” Detective Acting Inspector Securo said.

Police say they also understand there was “no violent incident” involved in the deaths of the two dogs and a cat found.

A forensic van parked outside a house with a black wall

A forensic van parked outside the house where the bodies were found. (ABC News: Keane Bourke)

A note was also left at the premises, which police are investigating.

Detective Acting Inspector Securo said the bodies of the family members were not found together.

“I can’t go into those details as to their exact location, however, I will say that they weren’t in the same location,” she said.

She said police were still trying to establish a timeline of events.

The call to police was received this morning, but it was not known when the tragedy happened.

“So what will form part of our investigation is — did this incident happen this morning?” Acting Inspector Securo said.

Aerial photos of a suburban street with white vehicles parked

Police vehicles line Mott Ct late on Friday morning. (ABC News)

“Did it happen last night? How long have those persons been in that house?”

Police say there is no ongoing threat to the community.

“Although this investigation is in its infancy, police are investigating this matter as a murder-suicide,” Detective Acting Inspector Securo said.

A police forensic van arrives at a street

A police forensic van arrives at the scene in Mosman Park. (ABC News: Keane Bourke)

“The situation is being assessed and a thorough investigation is being completed.”

Officers ‘in shock’

Detective Acting Inspector Securo said the officers who responded to the scene were “in shock”, and were being provided with support.

“It’s not often that our officers come across such a tragic event with this many persons deceased,” she said.

A heavy police presence is at the home, and several streets in the area have been cordoned off.

Police officers and vehicles on McCabe Street in Mosman Park.

Police let vehicles through a road block up the short street. (ABC News: Keane Bourke)

People are being asked to stay away from the area.

Neighbours who spoke to the ABC reported hearing emergency services arrive around 9am local time, and say it is out of character for the area.

Mott Close is a short cul-de-sac with only a handful of homes on it, in one of Perth’s wealthier suburbs.