"We are not sure yet why they were arguing, so we are trying to learn more about that as the investigation moves forward," Busch told PhillyVoice. Video shows the man step toward the security guard, who retreats, before appearing to reach for something on his chest — possibly a bag that appears to be slung across his shoulder. The security guard, who at this point appears to enter a fighting stance with his fists raised, takes a step toward the man and delivers one punch to his head. The man falls to the ground, and the security guard appears to land at least four more punches.