Basically I suggest these events occur even before the NPC is dead, if you shoot a combine with a shotgun in the chest they'll be knocked backwards and then get their footing and go back to attacking you, and you can stagger them as their recovering repeatedly until they die. This is might be too complicated but I thought it would at least be worth bringing up since my fav part of GTA was knocking NPCs down and watching them get back up.

Note: Idea is kinda similar to RagKnockdown Addon