What we know about how the Bondi Junction shopping centre ...

It started like a regular Saturday.

Hundreds of people flocked to a large shopping centre in Sydney's east to buy groceries, clothes and other items.

But as the afternoon stretched on at the Westfield at Bondi Junction, an emergency incident began to unfold.

While there is much that we don't know about the mass stabbing, such as the name of the attacker or what motivated him, there are some things we do know.

Warning: Some readers may find the following details of the attack, eyewitness accounts and footage of the incident distressing. 

We know police believe the attacker was a 40-year-old man but they are still waiting for formal identification. 

We know six victims — five women and one man — have died — five at the scene and a sixth in hospital.

We know eight other injured people are in hospital, some in critical condition.

We know one of the injured victims is a nine-month-old child.

And pieced together from what police and eyewitnesses have said, here's what we know about how the incident unfolded:

At 3:10pm, the attacker arrives at the Westfield shopping centre at Bondi Junction.

It is unclear where he goes, but police say he leaves the centre "very shortly after".

He returns 10 minutes later, at 3:20pm, and then begins to move through the centre, stabbing people.

Panicked shoppers begin to notice and many make triple-0 calls, alerting police, who have now received multiple reports about an incident.

One witness told the ABC they saw a man in a green shirt start stabbing others "indiscriminately".

As this is happening, shoppers call out for others to run. Some escape the centre and others shelter in stores.

Another eyewitness, Vernon Michael, said he saw a man armed with a large knife walking "calmly" and riding an escalator to a higher floor.

One person bravely stands at the top of the escalator and briefly holds off the attacker.

Responding police units are on their way, but it is the actions of an unnamed female police inspector who was already in the area that bring the stabbing spree to an end.

The officer was a "single unit", NSW Police Assistant Commissioner Anthony Cooke said.

Outside the shopping centre, people alert the officer to what is happening.

She enters the Westfield and makes her way towards where she believes the attacker is.

She tracks him and follows him to the fifth floor, walking "quickly behind him to catch up with him", according to Assistant Commissioner Cooke.

"[The attacker] turned, faced her and raised a knife," he said.

The officer shoots the man and he dies at the scene. Police have not said how many shots were discharged but some witnesses say they heard three shots.

It is about this time that other shoppers, some unaware of the stabbings, hear the gunshots.

Some panic, fearing there may be an attacker with a gun, and flee.

Shopping attendants lock down their stores with customers still inside and some help shoppers escape out exits in the back of storerooms.

By this stage, heavily armed police are at the scene and searching the area.

Riot Squad officers outside the shopping centre.(ABC News: Jack Fisher)

Reports there may be more than one offender turn out to be incorrect, with police later confirming the man shot dead by police had been the sole attacker.

So far, police say they do not know what motivated the man but there is no suggestion the victims were targeted.

The officer who stopped the attack has been hailed a "hero" by Prime Minister Anthony Albanese.

NSW Police Commissioner Karen Webb says the officer is "doing well under the circumstances".

"She showed enormous courage and bravery … we just talked [and] she's OK, her family is OK. She's got everything she needs for the time being."