Sydney stabbing accused Mert Ney had at least one appointment with his alleged victim Michaela Dunn before the rampage that shut parts of the CBD on Tuesday, a sex worker industry advocate says.

Key points: Police are yet to interview Mert Ney and no charges have been laid

Police are yet to interview Mert Ney and no charges have been laid The NSW Police Commissioner said establishing a motive was a "priority"

The NSW Police Commissioner said establishing a motive was a "priority" As part of the investigation, police will look into events up to 12 months before the incident

The revelation comes as police search for a reason behind the attacks.

NSW Police Commissioner Michael Fuller said establishing a motive was a priority and that Mr Ney's "potential link to terrorism" was concerning.

Mr Ney is still being held in Sydney's Royal Prince Alfred Hospital after surgery on his lower leg, and police are yet to interview him as they wait for a "toxicity issue" in regards to his drug consumption prior to the incident.

Mr Ney, 20, is accused of killing Ms Dunn with a kitchen knife before fleeing onto the street and stabbing Linda Bo, 41, as she was walking towards Darling Harbour.

Ms Bo was taken to St Vincent's in a stable condition and has since been released.

Police confirmed Mr Ney, who is yet to be charged, had visited Ms Dunn for sexual services on the day of the alleged attack.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 24 seconds 24 s Michaela Dunn was active on Instagram.

Scarlet Alliance Australian Sex Workers Association chief executive Jules Kim said she understood Mr Ney had seen sex workers, including Ms Dunn, on multiple occasions in the past.

"And there hasn't been incidents, certainly not with Michaela in the past as well," she said.

"It's not something that was at all expected or planned, from what I understand."

Ms Kim said the sex-work community was "deeply shocked" by Ms Dunn's death.

"We are mourning the loss of somebody who was really loved, who was somebody's daughter, somebody's sister and a great friend to many people," she said.

"She was also a sex worker but that was only a small part of her life."

Ms Kim said media reports suggesting that Ms Dunn was inherently at risk because of her job were misleading.

"It's not an expected part of our work and there was nothing that Michaela did that actually brought this upon her," she said.

Mert Ney is still under police guard in hospital. ( Twitter: David Vaux )

Commissioner Fuller said police were looking into "not just the crime but the lead-up to the crime".

"We'll go back six months, we'll go back 12 months if we need to, to look at the touch points of all levels of government," he said.

Yesterday, NSW Police established Strike Force Lalchere to investigate the circumstances of the attack and its inquiries will be supported by the Terrorism Investigation Squad.

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Police have so far resisted drawing any concrete connection between Mr Ney's alleged actions and terrorist activity.

However, Commissioner Fuller said the "potential link" to terrorism was an issue "we are all concerned about".

Police found a USB stick linked to Mr Ney suggesting he had "some ideologies" in relation to terrorism, and information of mass casualties from North America and New Zealand.

Commissioner Fuller said it was difficult to prevent this type of "lone actor" crime, which could have resulted in a "lot more" people dying.

Communication between government departments has come under criticism after it was revealed police were searching for Mr Ney while he was living in government housing.

In the days before the incident, Mr Ney presented at Blacktown Hospital in an agitated state and suffering severe mental health problems, but checked himself out six hours later.

Former NSW deputy police commissioner Nick Kaldas said the matter reflected a "profound policy failure" on the part of the state's mental health services.

A teddy bear tribute was left outside the apartment block where Michaela Dunn was stabbed to death. ( ABC News: Mark Reddie )

But Commissioner Fuller said dealing with mental health issues was "always a challenge".

"But the alternative would be to lock everyone up who presents with a mental health issue," he said.

"Again, I think there would be lots of people who would have family members and neighbours who actually get through life with help quite satisfactorily.

"Profiling every mental health person as someone who is dangerous, is more dangerous than the individuals, to be honest with you."