Sir Thomas Mitchell Drive, Davidson Google Maps

New South Wales police found two cylinders outside Fernando Manrique’s home on Sir Thomas Mitchell Drive in Davidson, NSW, on Monday. The cylinders led the police to uncover the elaborate system of gas chamber that could be the cause of death of Manrique and his family.

"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," an NSW police spokesman was quoted by the Daily Telegraph as saying on Tuesday.

On Monday, police discovered the body of Manrique’s wife, Maria Claudia Lutz, 43, with one of her children in one room. Manrique, 44, was found in a separate room. The second child of the couple was found alone in another room. The family's pet dog was also found dead.

Neighbours told the police that they saw Manrique working on the roof on Saturday. He pulled up the tiles in his roof but they had no idea that he had been setting up a gas chamber. The discovery of the gas chamber led the police to investigate the possibility of murder-suicide.

On the day of the incident, mothers at the St Lucy's Catholic Primary School in Wahroonga, where Lutz worked, reported the police that Lutz did not arrive for canteen duty.

Neighbours described Manrique as a loving father, while Lutz’s friends described her as an amazing mother and selfless person. Despite having two children who suffers from autism, the couple managed to have a happy family. Neighbours recalled that they saw the family together at the local playground where they appeared to be happy.

The couple's family in Bogota, Colombia, revealed that the couple's marriage was failing. An anonymous source told The City Paper in Bogota that there were times when the couple felt the stress of bringing-up the children, which brought tension to the relationship.

The police continue to investigate.