Hi! I'd say you need to use the spacebar or something on the right side of the keyboard for the action/shoot button. With WASD being used for movement you need the shoot button to be pressable by a different finger. Aim and camera change might be better on the right side of the keyboard too.
Also, it seems impossible to shoot the crawling zombie at the moment (even if you aim down).
It's a great concept though! Awesome work! :)