A Marine veteran who served in Afghanistan is being hailed as a hero for helping scores of people escape from an Orlando nightclub targeted by a terrorist.

When Imran Yousuf, a bouncer at the Pulse nightclub, heard the gunfire break out early Sunday morning, he told CBS News that recognized it immediately.

“You could just tell it was a high caliber,” said Yousuf, a former sergeant who just left the Marine Corps last month. That’s when his Marine Corps training kicked in, he said. He ran toward a locked door that people had huddled around, too terrified to move.

“I’m screaming ‘Open the door! Open the door!’” Yousuf told CBS. “And no one is moving because they are scared.