The screenshot bellow shows a zombie that randomly allied with my character for no reason (as far as I can tell) story bellow.

So, I was in an 8 player mf game running TZ ancient tunnels when I ran into dark elder in Lost city. I Killed his boss pack and refreshed my bo. But then I noticed something odd. I had given my bo and my auras to a zombie. I couldn't hurt it and it didn't tele around with me. The zombie started walking towards and attacking a fire tower.
I went to town and of course it didn't follow. When I came back it was still attacking the fire tower. The behaviour was similar to a returned from faith bow or tomb reaver. I have never seen anything like this. Also notice this is not a revive. I have no revives in my party and he isn't even the right color.
Has anyone ever experienced something like this? Please let me know if you have details about this behaviour. It's fascinating.