Want an animated rig to behave like physics body

What I’m trying to do:

I have a character rig (is animated by Kinect) and it should fall down like a normal physics body (and collide with the static world).
So he can still move and fall over.

This is an image for understanding:

26536-testscene.jpg

Another way to solve my problem would be: How to freeze a ragdoll and behave like a physical object.