So I pulled my trusty DBA board (24" x 24") out of retirement and placed some scenary.
Brian once again runs, this time using the car as a barrier. His second action is to shoot the nearest zombie (note a replacement die was used for the zombie die roll). Head shot Boom!
Scampering towards the tent Brian again turns and fires, knocking down a walker, but attracting a lot of attention. The walkers stumble into the tent.
Brian, stressed beyond his limit screams. This pushes the threat level to the end point and the game ends.
I am not sure if the shoot and scoot tactics worked, i will have to try it again and see if I can do better.