The apartment block where a mother and her son have been found dead. Picture: Daniel Aarons.

Police and paramedics raced to Grace Campbell Crescent in Hillsdale around 1.30pm, when neighbours say they immediately shut off the supply of gas to the building.

Police confirmed an operation is still under way and neighbours have been left stunned.

Police investigate the scene in Hillsdale, where a gas leak was detected. Picture: Daniel Aarons.Source:News Corp Australia

Aiden Yousif said the woman was known to locals and had previously smashed a number of car windows in the street.

Gas technicians remain at the scene, police have taped off the apartment block and detectives are combing the unit at the top of the four-storey building.

Another neighbour, Syarif Suharto, said the community was in “shock” over the boy’s death.

“He seemed like a happy boy, he was hanging around at the park and so on,” he said.

“It’s very tragic to have something like this happen in our area because our area itself is very quiet.”

Originally published as Mum and son, 4, found dead