A full investigation into the mental health system will be carried out after a Sydney father accused of stabbing his son to death was denied care just weeks before the incident.
The 36-year-old man allegedly stabbed his five-year-old son in his bed at their Carlingford home in the city's northwest on Friday morning.
The boy's mother, a nurse, has now told The Daily Telegraph she had previously begged health authorities for help for her "sick" husband, who cannot be named for legal reasons.
"The death of my son is the price I'm having to pay for this," she said.
"He loved our son more than words can express. He was the apple of his eye and he couldn't wait for the day he was born."
His grandmother says she allegedly found the boy in bed with his dad.
"I know he needed me, but my grandson needed me more," she told the Seven Network on Tuesday.
"I can't be in two places at once, there's only one (of) me."
The Northern and Western Sydney Local Health Districts said on Tuesday there would be a full investigation into the ongoing care and treatment of the man.
"The loss of the little boy last week is a tragedy and we extend our deepest sympathies to his family and friends," a spokeswoman said in a statement.
The investigation, to be carried out by NSW Health chief psychiatrist Dr Murray Wright, will examine the man's ongoing care, including the period leading up to the boy's death.
Premier Gladys Berejiklian said "no stone will be left unturned" in the investigation.
"We want to know what happened and if there's anything more we need to do to support people with mental health (issues) moving forward, we'll do that," she told reporters in Sydney.
Labor leader Luke Foley said there were major issues in the state's health system.
"We owe it to that little boy that this is investigated independently and improvements are made," he told reporters in Sydney.
Mr Foley cited record waiting lists at emergency departments and for elective surgery as further signals the system is struggling.
"The premier and the treasurer keep boasting about budget surpluses," he said.
"How the hell is it that there's this lack of resources devoted to mental health when you see the saddest, most tragic event in recent days."
The father has been charged with murder.
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