A man arrested after the death of his mother had been charged and hit with a restraining order only days earlier, police say.
The man remains under police guard in hospital after the 67-year-old woman's body was discovered by fire crews at a home in Sydney's southwest on Sunday evening.
Police arriving at the residence were confronted by the 31-year-old man wielding a kitchen knife.
Officers deployed a taser and he was arrested. It was the second time in three days police had taken him into custody.
"Police responded to an incident on Friday and as a result of that incident, the male person was charged and an AVO (apprehended violence order) was taken out," Detective Superintendent Martin Hayston told reporters on Monday.
Inquiries into his potential involvement in her death are ongoing.
Det Supt Hayston said the woman was found with "significant head injuries".
"There is a lot for us to unpack to determine how things played out yesterday evening," he said.
The first sign of something awry was when neighbours noticed a small blaze at the rear of the home on Wattle Street in Bankstown about 7pm.
Fire crews extinguished the blaze and discovered the woman suffering serious head injuries, then called police.
She died at the scene.
After stunning and cuffing him, police took the son to Bankstown Police Station and then transferred him to hospital for assessment.
No charges over his mother's death have been laid.
