"It took two eventful tours in Vietnam, a handful of medals, a knee full of shrapnel, and an honorable discharge before the unthinkable happened: Bill ran out of wars. But now an army of infected has declared war on humanity. After decades of aimless drifting and dead-end jobs, Bill's finally gotten back the only thing he ever wanted: an enemy to fight." - Official survivor description

Bill is the leader of the group who plays the role of Zoeys adoptive father after her mother died and turned into one of the infected and put down her father

Bill should sound like a senior war veteran with a kinda gravelly voice Left 4 Dead Bill Quotes [All] (youtube.com)