You were trying to run away from some infected - you might be half infected, but the zombies still chase you to try and fuly infect you - you're a lucky one that has some sort of immunity when you got bitten, you fall through a vent, and as you make your way out, you're face to face with a person with a gun pointed at you. the roles are reversed so you are the furry, and the person is the one you've gotten deal with, or you could change how it starts if you want