A family of four, including two children with autism, who were found dead in their northern Sydney home, died as a result of a murder-suicide, police say.
The bodies of Colombian nationals Fernando Manrique, 44, Maria Claudia Lutz, 43, and their two children, Elisa, 11, and Martin, 10, were found yesterday morning when police forced entry to the family's Davidson home.
Police said it appeared the family died of gas poisoning and were asking the public for help to discover the motive behind the deaths.
Neighbours said the children were lovely and kept to themselves.
Flowers have been laid outside the home as friends payed their respects.
Neighbour Janine Akers urged anyone who needed help to ask for it.
"If you're feeling like that just get help, we're all here, especially in a community like this," she said.
"If someone is struggling, get help."
The children went to St Lucy's primary school in Wahroonga.
Acting principal Warren Hopley said yesterday staff were in shock.
"The teachers … we're just all very upset," he said.
"The children had very high complex needs … I don't think [their mother] slept for many hours of the night because of the difficulties often with the two children."
A NSW Police statement said they had no visible injuries and they were awaiting the results of toxicology reports.
"Whilst the cause of death will be a matter for the coroner to determine, police are looking at the possibility the family members died from the introduction of an airborne gas," it said.
"It is early days in the investigation and investigators will need to wait for toxicology results and results of the post-mortems to determine cause of death.
"Forensic police continue to recover evidence from the home in Davidson."
A large dog was also found dead at the house.
A crime scene is still set up at the home and detectives are back today, searching the backyard and the house.
The homicide squad was looking into the matter, but have handed investigations back to the Northern Beaches Local Area Command.
"Strike Force Josselyn has been established with the assistance of State Crime Command's Homicide Squad to investigate the deaths," a statement said.
Northern Beaches Police Superintendent Dave Darcy initially said they were keeping an open mind as to whether they were searching for a suspect, but police have since ruled out this possibility.
Superintendent Darcy said the family were valued members of the community.
"The mother in particular is held in very high regard in the community," he said.
"Since coming to Australia they've made a significant contribution to how we live, they've done a fantastic job."