dont listen too carefully to the narrarator... and if you do, take it with a grain of salt, but the point of me linking this, is to demonstrate that pistols are predators and will indeed kill shrimp and crabs if they are hungry (and big) enough. Ive heard of one pistol that even killed off a mantis.
http://www.youtube.com/watch?v=eKPrGxB1Kzc