Agree with both the above. In my experience - occasionally while killing totterings, they would "Call for help" - except for me, upon their death this mob would come charging in at me from a distance away (read out of agro. range)as opposed to "next to me". Kinda neat actually - something that really did seem to be "working as intended".
This is another of the special "Call for Help" mobs like the Sarnak Enforcer from The Overthere that were put into the Hot Zones. Attack a live gorilla and there is a chance it will "Call for Help" and this guy will spawn next to you. It seems it's only the live gorillas, normal looking black ones, not the hideous looking undead ones, that I've seen "Call for Help" They are a bit tougher and higher level than the average zone mob and so far have always dropped the neck or shard.