What will they do if you kill the biggest and baddest of the group? They're coming for him.
If you drop one, and others are anywhere around, you'll probably have one or two come for the recovery. What you may not see is the two or more flanking you. This is how they live - they're practicing predators who hunt together, and that move is just natural ambush tactics, but to them it's a most natural reaction.
Like a big cat likes to take prey from behind and above. It's automatic. Not a lot of thinking to it. Difference is, these BF critters can do some thinking in addition to their well practiced tactics.
I don't know that they fear death like us. I see a squirrel instinctively shimmy when one gets too close - a deer will bolt - a fish will flash out if he sees you - that's not a fear of dying - which would require a self-realization, but more of a survival instinct.
I don't know why scores of monkeys will throw their own feces from high in the trees if one is just passing through. They're territorial, and they will make it rain feces.
BF's play checkers. You better be playing chess, and be about three moves ahead.