Delci wrote:
That sub-boss is known as Disbeliever. If you shoot it down fast enough (under the circumstances you did), its companions won't appear.
According to the Tactical Reference Guide, it's a combination of multiple lifeforms and machines, and can link up with others like it (leadership ability, there's only about three of them in existence). When you kill the first one fast enough, it can't call for help so you don't have to fight the other two.
I just love it how you can always find a suitable explanation.
