Yeah those virus-controlled guys still attack you when you destroy the heads, thats actually part of the game later on. But I'm talking about odd occurances when you destroy the head and they're still moving towards you in which they will fall and die shortly after, BUT in certain cases they actually attack you as if they still have a head attached on! Thats what caught me by surprise...cause i was assuming they were just going to dropped dead in front of me. And this was early on before they started doing the virus thing. Pretty frickin weird.....its got to be glitch :(