because i experiment to this npc and i think.....hmmm what happent i spawn no more room in hell infected and i spawn left 4 dead 2 npc in to one map? its a they are
not attacking each other and they are its very stronger because if you getting attack by nmrih infected your movement will slow and attacked by l4d2 legular or special infected its look like a you walk on a pile of nails(its preaty over power)