A HIDDEN network of pipes were used to funnel gas into the home where a father, mother, two children and a dog were found dead in Sydney's north this week.
The family patriarch Fernando Manrique is understood to have rigged up the elaborate system, with even neighbours confirming they recall him working on the roof with power tools.
They could have no idea of what he had planned.
Mr Manrique's wife Maria Claudia Lutz, 45, was found dead alongside daughter Elissa, 11.
Their son Martin, 10, was found in another room.
Mr Manrique was found on his own elsewhere in the house, as was the family German Shepherd.
NATIONAL 24/7 CRISIS SERVICES
News Corp reports detectives are now investigating the source of the poison found in gas canisters.
Police were also now pulling apart the piping that fed the family the ultimately fatal dose of toxins.
Its understood Mr Manrique was working on the roof of the house in the days before the deaths occurred.
Police believe he has installing the system to distribute the poison, which included several devices throughout the house.
It was "extensive, elaborate and well-planned", according to police sources who spoke to News Corp.
Mr Manrique worked as an executive for a technology company, while his wife was a dedicated and devoted mother to their kids, who each lived with autism.
The Daily Telegraph reports family members in their home city of Bogota in Comobia said the parents were on the verge of divorce.
Update your news preferences and get the latest news delivered to your inbox.