SYDNEY, Dec. 29 -- When the shots rang out at a Hanukkah gathering on Sydney's Bondi Beach, Ahmed al-Ahmed did not think of heroism. He thought of stopping the killing.

In verified footage from the attack, the Sydney shop owner, born and raised in Syria, is seen tackling one of the two gunmen from behind and wrenching a long gun from his hands.

Speaking in an exclusive interview with CBS News, Ahmed described the split second that propelled him forward.

"I hold him with my right hand and start saying a word, you know, like to warn him - 'drop your gun, stop doing what you're doing'," the father of two said.

The attack on December 14 left 15 people dead and 40 injured in what police have declared a terrorist incident targeting the Jewi...