The woman who called emergency services is said to have lived alone in the unit where the stabbing took place and is related to the man.
The man’s partner, who was not at the scene, speaks to the police.
“We urge anyone who witnessed or heard of an incident at this location to contact Campsie Police or Crime Stoppers,” Waldau said.
“Any type of incident involving a young child is always tragic… Our condolences go out to the child’s extended family.”
Photos of the scene showed officers entering the complex while crowds gathered on the footpath outside.
Teams of paramedics and police officers in uniform and plainclothes were seen rushing into the building. Local residents gathered outside as the police helicopter circled overhead.
Anyone with information is asked to call the police or criminal investigation department on 1800 333 000.
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