You mix up some hazardous chemicals

You really missed your calling. You should have been a chemist. You brilliantly make a weapon that uses mostly salt as a component. It sprays and a cloud of salt laced chemicals attach to all living flesh and the people are converted literally into pillars of salt! You just march in one Sunday with a large tank of the stuff. You aim the hose and flip the button. A rush of white fumes cover the worshipers in the pews. All the liquids are evaporated, the bones dissolve. Whats left appears to be nothing more than a pillar of salt with slightly human like features. You killed them all this way. You leave the pillars where they sit or stand for now. They look pretty cool! You start to set up your own church here now...