open the door

You slowly approach the door and slide the boards from the door. You slide the door open a bit. A scene of utter destruction greets you. The neighborhood is empty, houses are broken down or on fire. You poke your head out the door a bit more. The direction of where the noise had come was not evident. What is most evident is the lone zombie, shambling brokenly towards you. Panicked, you know you have two decisions. Should you shoot it, or slam the door?