An idyllic summer afternoon on crowded Bondi Beach has turned into one the darkest days in the country's history.

Australia's most iconic tourist destination was rocked by a mass shooting on Sunday as two men stood on a pedestrian footbridge and opened fired into crowds of locals, holidaymakers and families.

Some had been there to celebrate Hanukkah, the Jewish Festival of Light, which police believed was the intended target of the massacre that has been officially designated a terrorist attack.

In just a few short minutes the gunmen took the lives of 11 innocent people, though that number could rise. NSW Police Commissioner Mal Lanyon also confirmed at least 29 people had been injured.

One of the gunmen was also shot dead and the second has been hospitalised.

Prime Minister Anthony Albanese gave a speech to the public following a meeting of the National Security Committee on Sunday night.

'There is no place for this hate, violence and terrorism in our nation,' he said.

'Let me be clear we will eradicate it. Amidst this vile act of violence and hate will emerge a moment of national unity, where Australians across the board will embrace their fellow Australians of Jewish faith.

'At this dark moment for our nation, our police and security agencies are working to determine anyone associated with this outrage. Our agencies will provide you with factual updates as quickly as possible as they continue to emerge.'

The praise for first responders has been unanimous from leaders across Australia, but some witnesses have questioned why police did not have systems in place to respond to an attack such as this far more swiftly than what unfolded.

Especially after the Westfield Bondi Junction stabbing attack that unfolded not too far away.

It has also since been admitted by Australia's domestic security intelligence agency, ASIO, that one of the shooters was on their radar.

'One of these individuals was known to us, but not in an immediate threat perspective,' ASIO Director-General Mike Burgess said.

'So obviously we need to look into what happened.'

How the attack unfolded

Two gunman arrive at Campbell Pde on the edge of Bondi Beach and exit their vehicle. A black flag ISIS-style flag was seen draped over the hood of the car.

Video footage shows them making their way to a pedestrian footbridge and opening fire towards a grassy area known as Archer Park.

A community festival celebrating Hanukkah was being held in that vicinity. The Chanukah by the Sea event was a family focused gathering to celebrate the first day of the eight day Jewish Festival of Lights.

Beachgoers run for their lives

Witnesses reported hearing loud bangs and seeing people injured and bleeding.

People then begin to realise what is happening and try to get out of the area, leading to a rush of people cascading off the beach.

6:47pm Dozens of police cars and ambulances head to Bondi Beach following reports of a mass shooting.

Mobile phones begin to light up checking on people at Bondi.

Worried posts appear on the popular Bondi Local Loop Facebook group asking what is happening at Bondi.

7.05pm: NSW Police issue an urgent warning for people in Bondi to take shelter. All other members of the public are told to stay away from the area.

Gunman disarmed and taken down

About 7.20pm: One of the gunman has moved off the footbridge and along a cement sidewalk that runs between the car park and Archer Park where the festival is being held.

He is rushed by a member of the public who crouched behind a car to sneak up on the gunman before grabbing his weapon and turning it back on him. The civilian has since been widely hailed as a hero. A second bystander is believed to have assisted him.

After the attacker has been disarmed, police swoop. The two gunmen are shot. One would later be confirmed dead and the other hospitalised.

7.30pm: Footage shows two men lying on their stomachs on the footbridge and not moving as they are handcuffed by police. Bystanders can be seen screaming at them.

7:43pm: NSW Police confirm two people have been apprehended.

8:35pm: NSW Ambulance confirm 16 patients are in hospital.

8.45pm: NSW Police confirm 10 people died, including one of the shooters. The other shooter is hospitalised in critical condition. This number is later revised to 12.

9pm: Police establish an exclusion zone around the scene. It confirms officers are investigating several suspicious items.

These are later confirmed as improvised explosive devices (IEDs) located in the shooters' car. A massive police presence stays in the area going from car to car searching for more devices and a potential third gunman.

Police conduct raids

It is confirmed police are conducting raids around Sydney linked to the shooting, suggesting there could have been existing intelligence on the men.

9.20pm: Police raid the home of one of the gunmen in Bonnyrigg.

9.30pm: He is identified as 24-year-old Naveed Akram.

10pm: NSW police commissioner, Mal Lanyon, confirmed 29 people have been hospitalised in a 'range of conditions'.

10.15pm: Albanese condemns the attack as an 'act of evil anti-Semitism' and 'terrorism'.

About 11.30pm: Two people are arrested at Bonnyrigg.

Around the same time police say they have secured Bondi, contained the IEDs and there is no further threat. The area remains a crime scene.

Questions raised about the police response

One witness Grace Matthews heard the shots as she walked to the Chanukah by the Sea event. She sheltered in a nearby church.

'One of my friends was at the festival (and) he said the police were just very underprepared to respond to this kind of a threat,' Ms Matthews told the ABC.

'So that was why it required a member of the public, like a civilian, to neutralise one of the threats.'

'There should never be a situation where a member of the public - or even a plainclothes policeman - is in a shootout with an active gunman.'

'There's a police station less than a block from where the shooting was happening ... it's beyond my understanding as to why it took so long to handle.'

Commissioner Lanyon has defended the response of NSW Police and said he was 'incredibly proud' of the way the tragedy was handled.

'They have done a fantastic job, and unfortunately, after the Westfield Bondi Junction attack, we have learned a lot and tonight ambulance and police and other responders acted promptly and professionally to do a great job.'

The fallout

ASIO's director-general has said his agency will examine how someone on an apparent watchlist had been able to carry out such an attack.

How the two gunman were able to obtain the high-powered weapons remains a burning question.

NSW Premier Chris Minns has declared there will be a 'massive and complex' investigation.

'This just beginning investigation. And there are things that tonight we don't have the answers to.

'However, we do have answers to some crucial pieces of information for our wonderful city and our beautiful state.

'The first one is the outpouring of love and support from ordinary Australians, for Australia's Jewish community is real.

'Secondly, today is another example of the enormous pressure and responsibility the danger that NSW Police regularly face as part of their job. They do it without faltering. They didn't falter. Today we need them.

'And thirdly, tonight acts of personal courage and bravery from individuals in our community. And I think it's worth remembering that in all of this there are still wonderful, brave Australians that are prepared to risk their lives to help a complete stranger.'