Damage animation with ragdoll

I need to animate my own animation for a character rig with a ragdoll attached.
But I can’t make the animation when I animate a body part it will reset the keyframe to 0 immediately.
So how can I make a hit animation when I hit my zombie with a raycast.

How about an extra animation layer on top, you can have multiple animations running on the same model/character, with a set blend value between the animations.
You can run the rag-doll on one layer, and the bullet hits on another layer.
Layers :- Unity - Manual: Animation Layers
Blend TRees :- Unity - Manual: Blend Trees