A bystander tackled and wrestled a gun from one of the two alleged gunman during the Bondi beach mass shooting in which at least 12 people were killed, footage shows.

Video of the scene shows the alleged gunman standing on a footpath between a grassy area and parking lot holding a shotgun and firing into the distance.

The bystander, who is crouching behind a parked car, rushes towards the alleged gunman as he fires. He leaps on to the alleged gunman and wrestles the shotgun from his hands.

The video shows the alleged gunman falling to the ground before the bystander points the shotgun at him as the alleged gunman backs away.

As the alleged gunman retreats, the bystander gently places the shotgun against a tree and puts his hand in the air.

At least 12 people were killed in the attack on a Hanukah celebration, including one of the shooters, police said. At least 29 people were taken to hospital.

Authorities declared the incident a terrorist attack.

“This is a targeted attack on Jewish Australians on the first day of Hanukah, which should be a day of joy, a celebration of faith,” the prime minister, Anthony Albanese, said at a press conference on Sunday night.

“The evil that was unleashed at Bondi beach today is beyond comprehension and the trauma and loss that families are dealing with tonight is beyond anyone’s worst nightmare.

“Australians have had their lives cruelly stolen and many have been injured … Our first thoughts are with those in the terrible early hours of their grief.

“We are also thinking of everyone being treated for their injuries and many of whom are alive right now because of the courage and quick action of the NSW police and the first responders who rushed to their aid – as well as the courage of everyday Australians who, without hesitating, put themselves in danger in order to keep their fellow Australians safe.

“We have seen Australians today run towards danger in order to help others. These Australians are heroes and their bravery has saved lives.”

A separate video seen by Guardian Australia showed two men in black clothes crossing a bridge at the beach and firing. Multiple shots could be heard and people could be heard screaming.

NSW police confirmed the dead included a man believed to be one of two gunmen, with the second alleged shooter in a critical condition. They were also investigating whether there was a third shooter. Two police officers were among the injured, police said.

The NSW premier, Chris Minns, told media on Sunday night: “This cowardly act of terrifying violence is shocking and painful to see, and represents some of our worst fears about terrorism in Sydney.”

Minns recognised the “extraordinary acts of personal courage and bravery from individuals in our community”.

“I think it’s worth remembering that in all of this evil, in all of this sadness, there are still wonderful, brave Australians that are prepared to risk their lives to help a complete stranger,” he said.