Make you're own animation, or buy the 2º or 4º model pack for FPSC.
You can't use other games media (including animations).
You can, also reqwest an animation to any modeler (including myself) to make it for you, but, be prepared to pay, since a good looking animation isn't easy to make and takes lots of effort, but, who knows? Xmas is almost there, someone might open his heart.
There are lot's of free tutorials on google, wich teach how to rig and animate humanoid models, after you learn them, you can easely pick up Dawn of The Dead, Resident Evil, etc., etc., etc.helf, watch it, to see how the zombies move, so you can make a close to "reality" zombie animation.
My love is seperated in 2 parts, 1 of them is 3ds Max 7, the other; FPSC.