NSW to review accused stabber's history

Mert Ney, accused of the Sydney stabbing attack, is yet to be charged and is still in hospital

The NSW government is reviewing how agencies dealt with a young man in the weeks before he allegedly murdered a sex worker in a Sydney apartment and went on a CBD stabbing rampage.

Mert Ney is accused of killing 24-year-old Michaela Dunn in a Clarence Street apartment on Tuesday before allegedly stabbing 41-year old Linda Bo at the Hotel CBD.

He was later restrained by onlookers after running through the city streets brandishing a bloodied kitchen knife.

The 20-year-old remains under police guard in hospital and is yet to be charged.

His sister, who asked not to be named, on Wednesday apologised for her brother's actions, telling media he was suffering several mental health issues.

She described a recent "descent into insanity".

Ney's family reported him missing following a domestic dispute last week. It's understood he sought medical treatment about that time.

NSW Health Minister Brad Hazzard and Mental Health Minister Bronnie Taylor described the circumstances as "tragic" and have ordered a review.

"As with any critical incident, NSW Health will be reviewing all aspects of the care and treatment of the alleged perpetrator," they said in a joint statement.

The outcomes of the review will be provided to the ministers.

The NSW opposition says it's concerned communication between departments broke down, following a News Corp Australia report that Ney was staying in government emergency housing while police were searching for him over a domestic violence incident.

"I don't want a situation where agencies in isolation are reviewing their practices when we need a system that works in a coordinated way, a meaningful way, to protect the individual, to support their family and, just as importantly, to support and protect the community," Labor health spokesman Ryan Park told reporters on Thursday.

Meanwhile, lawyer John Bamford has broken his silence, revealing he was the city worker - since dubbed "chair man" - who approached Ney before his arrest.

Mr Bamford told the Seven Network on Thursday he was getting lunch when he saw the 20-year-old with a knife raised.

"I just grabbed the chair and, you know, went after him basically as best I could," he said.

"What am I going to do, go home and say I was there and I could have done something and backed away from it? I mean there was just ... there was no option."

Ms Dunn has been remembered as an "incredible" woman by family and friends.

Police believe Ney attended the Clarence Street unit to see the 24-year-old for "the purposes of prostitution". She was later found with a slashed neck and pronounced dead at the scene.

Ms Bo, who Ney allegedly stabbed in the shoulder, was released from hospital on Wednesday night.

Investigators are still trying to piece together why Ney - who had a history of mental illness - launched the attack.

He was allegedly carrying a USB stick with information about recent mass casualties in New Zealand and the United States, and could be heard on video footage shouting "Allahu akbar".

NSW Police have not classed the attack as a terrorist incident and have not identified any links to terrorist organisations.

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