Joel Cauchi, 40, fatally stabbed six people and injured at least 12 more in a violent rampage at Westfield Bondi Junction on Saturday afternoon.

NSW Premier Chris Minns said many people showed instinctive bravery and ran towards danger including Inspector Amy Scott, who he said saved many lives by shooting Cauchi dead at the scene.

"We're very, very grateful for the men and women that stood up in Bondi Junction," he said on Sunday.

NSW Police Commissioner Karen Webb echoed Mr Minns' sentiment and commended the state's first responders for their efforts.

"My thoughts go out to those people that were in the shopping centre, and as the premier has said, showed a great deal of courage yesterday." she said.

NSW Police Assistant Commissioner Anthony Cooke said the man was known to authorities in his home state of Queensland.

"We have received no evidence ... no intelligence that we have gathered that would suggest that this was driven by any particular motivation, ideology or otherwise," he said.

Queensland Police acting assistant commissioner Roger Lowe said Cauchi was living as an itinerant, relocating often across the state.

Cauchi had no known employment or partner and moved to NSW in March.

"We believe he has been sleeping in a vehicle or backpackers according to the family's information," Mr Lowe said.

His family only had periodic contact with their son, Mr Lowe added.

In a statement, Cauchi's family said they were devastated by Saturday's traumatic events and sent their thoughts and prayers to the families and friends of those killed and victims still receiving treatment.

"Joel's actions were truly horrific, and we are still trying to comprehend what has happened," the statement read.

"He has battled with mental health issues since he was a teenager."

They had "no issue" with Insp Scott shooting their son, saying she was only doing her job to protect others and hoped she was coping alright.

Mr Lowe said Cauchi had not been arrested or criminally convicted in the past four to five years but was known to police.

Six people, five women and one man, were killed in the attack.

Four women aged between 20 and 55 and a 30-year-old man died at the scene.

A fifth female victim, 38-year-old osteopath Ashlee Good, died at St Vincent's hospital on Saturday night.

Dr Good's nine-month-old daughter was stabbed in the attack and is in a critical but stable condition at Sydney Children's Hospital.

Others killed included Dawn Singleton, the 25-year-old daughter of multi-millionaire businessman John Singleton, security guard Faraz Tahir and 55-year-old Pikria Darchia.

Two of the six victims were from overseas and had no family in Australia, Mr Cooke said.

At least 12 others, including nine women, two men and Dr Good's daughter, were taken to hospital after suffering stab wounds in the attack.

Prime Minister Anthony Albanese said Ms Scott, who was lunged at by Cauchi before he was shot, no doubt saved lives.

Mr Albanese joined Mr Minns and local MP Allegra Spender to lay flowers at the scene on Sunday afternoon.

Federal Opposition Leader Peter Dutton said there was heroism amongst the horror.

Ms Webb said Insp Scott was doing well under the circumstances.

"She showed enormous courage and bravery," she said.

"It was an awful situation ... but it could have been much worse."

The shopping centre remained closed on Sunday but some shoppers were able to retrieve their cars.

Australian Associated Press