Two teenage brothers are believed to have been killed by their parents in a double murder-suicide in Perth’s west.

The bodies of Leon, 16, and Otis, 14, were found at the family’s Mosman Park home about 8.15am (AWST) today after a person known to the family became concerned for their welfare.

The bodies of their parents, mother Mai, 49, and father Jarrod Clune, 50, were found in different parts of the property, along with a note, police said.

Leo, 16, and Otis, 14, were found at the family’s Mosman Park home (Nine)

Two dogs and a cat were also found dead, police said.

“This is a highly distressing situation for all involved, from community members to the person who located the family to our first responders,” Detective Acting Inspector Jessica Securo said.

She said there was “a note that was left at the premises, though I’m not able to go into the content of that letter”.

“It will form part of our investigation.”

Police have not revealed how the family or their animals died, but said it appeared there was no violence.

“There was no weapon used during this incident and the family have no reported family violence matters with police,” Securo said.

The bodies of parents Mai, 49, and Jarrod Clune, 50, were found in different parts of the property. (Nine)

Police said they were aware that the children had experienced “significant health challenges”.

It’s understood the boys lived with severe autism and one was non-verbal.

“Although this investigation is in its infancy, police are investigating this matter as a murder-suicide,” WA Police said.

“This tragic incident occurred only this morning and it will take time for police to investigate the circumstances.”

Police at the scene of a major incident at Mosman Park. (Kelly Haywood/9News Perth)

Friends of the couple told 9News they were shocked and said Mai and Jarrod were devoted parents.

“The boys were beautiful,” one friend told 9News in a statement.

Leon and Otis had attended Christ Church Grammar School. The principal today told the school community their thoughts and prayers were with family and friends.

Securo urged anyone who felt affected by the tragedy to “speak to your loved ones and get some help and assistance”.

“WA Police Force has engaged our health and welfare and support services for all our front-line staff who attended this incident,” she said.

Readers seeking support can contact Lifeline on 13 11 14, or beyond blue on 1300 22 4636.

National Sexual Assault, Domestic Family Violence Counselling Service 1800RESPECT (1800 737 732).