Hells Angel in Australia was killed Saturday afternoon during a 10-man brawl involving bikers of his group and members of a rival motorcycle gang inside the Sydney Airport.Police arrested four men involved in the melee that killed an unnamed 29-year-old man from southwestern Sydney. The man died in a hospital after his head was repeatedly smashed with metal posts by men of the Comanchero club, according to police.Other suspects escaped from the terminal by riding on taxis.An investigation in under way to determine what caused the deadly brawl witnessed by many travelers at the airport's domestic terminal.