A Sydney fruit shop owner who wrestled a gun from one of the alleged attackers during the mass shooting at Bondi Beach is recovering in hospital after undergoing surgery for bullet wounds to his arm and hand, his family said.

Forty-three-year-old Ahmed al Ahmed was identified on social media as the bystander who hid behind parked cars before charging at the gunman from behind, seizing his rifle and knocking him to the ground.

Australian police on Monday said a 50-year-old father and his 24-year-old son carried out the attack at a Jewish celebration at Bondi Beach on Sunday afternoon, killing 15 people in the country's worst mass shooting in almost 30 years.

Ahmed's cousin Mustafa told 7News Australia that doctors had informed the family that Ahmed was stable following surgery.

"He is a hero, he is a 100% hero," Mustafa said.

"Still he is in the hospital and we don't know exactly what's going on inside ... but we hope he will be fine."

Also Read: Father, son behind Australia Bondi shooting that killed 15: Police

Tributes have poured in from leaders both abroad and at home.

US President Donald Trump called Ahmed "a very, very brave person" who saved many lives. Chris Minns, the premier of New South Wales state where Sydney is located, has hailed him "a genuine hero" and said the video was "the most unbelievable scene I've ever seen".

A GoFundMe campaign has been set up for Ahmed with just over A$200,000 ($132,900) raised in a few hours. Billionaire hedge fund manager Bill Ackman was the largest donor, contributing A$99,999 and sharing the fundraiser on his X account.