Alleged Sydney knifeman Mert Ney had met Michaela Dunn at least once before the Tuesday rampage, according to a sex industry advocate.

Jules Kim, the chief executive of Scarlet Alliance, one of Australia’s leading sex worker advocacy groups, told the ABC the pair had met for at least one previous appointment, and Ney had met with sex workers on multiple occasions.

“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.”

Ney allegedly killed the 24-year-old Ms 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 rampaging through the city streets with a bloodied kitchen knife.

Ms Kim said the 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.”

The sister of the 24-year-old, lawyer Emily Dunn, said the grief-stricken family was still trying to process what happened.

“We didn’t know, anything, we’re trying to grieve, we’re all in shock and trying to come to terms with all that’s happened,” she told The Daily Telegraph through tears.

It is believed Ney made an appointment with Ms Dunn at her Clarence Street unit with the promise he would pay.

Investigators are now trying to piece together why Ney — who had a history of mental illness, homelessness and drug use — launched the attack.

Earlier this week, NSW Police Commissioner Mick Fuller said Ney went onto the street to “kill more people”.

However, he said Ney’s criminal history was “not remarkable”.

“He has some low-level issues around theft, malicious damage,” he said. “He had some domestic violence issues linked back to his family that, again, were not significant or serious injuries.

“However, they were being investigated. But if you look at his spreadsheet from a criminal history perspective, it remains unremarkable.”

He added that Ney was listed by his family as a missing person.

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.

Ney 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.