My crested oyster goby tries to kill the pistol shrimp whenever it sees those claws. I think it might be angry at the pistol for shooting it when the oyster goby got into a territorial dispute/really angry argument with the wheeler shrimpgoby. Whatever it is, this goby puffs up and looks angry whenever it comes out of the rockwork, and it chases anything that gets near it. Gobies are supposed to be peaceful.