They know you are an Admin now so,they came back to life just to bother you with needing help ......lol. is it possible that maybe as you were killing the last of them,one of the Shamans brought it back to life? never seen this happen before at all.
photoshop ) , kidding .... i have seen this before, there are alot of bugs in this game ... old outdated soft
Nice bug , it`s the same thing, sometime in baal hell when you kill all the monster at the start on throne and go after minions in back you will see one monster but you killed them when you enter