Nah. They don't kill every worm they see, either. They'll just occasionally kill and eat a small crawling worm that's in their burrow, like the little scavenging worms you see now and then. Maybe a baby bristleworm sometimes. They don't eat enough to put a dent in anything's population. I think pistols are mostly detritivores?
They aren't dangerous to your tank's inhabitants most of the time. If something else crammed itself into the burrow and harassed it, the pistol might eventually do some damage shooting at it. They won't come out and go after cleaners or anything. I guess a starving one might eventually? But a starving anything will do something drastic.
Make sure to give it lots of bits of stuff. Break up some clam shells into little pieces and scatter those around wherever it sets up shop, that sort of thing. Pistol shrimp love to build with small supports they can use to shore up their tunnels, and are surprisingly strong. It's amazing to watch. They're almost completely blind, but can build by touch.