you will basically want to have two meshes on your character when it spawns, one visible and one invisible and do the same for collision. then when the character dies and ragdolls or whatever detach the alive mesh from the character so it stays put and then toggle the vis and collision of the hidden mesh. those are the basics to it and there are many other ways to go about it.
another method you may want to look into that may be easier is to spawn in a new character when the player dies and just posses the new character. the posses node comes from the player controller.
