A vigilante is someone who is not a law-enforcement officer who takes it upon themselves to enforce the law. If these guys were walking up and down the street looking for law breakers and then shot someone they found sticking up a store, they’d be vigilantes. Shooting someone in self-defense when they came to you and tried to rob you is not vigilantism.
The sheriff should be made to work the late shift - unarmed - at a crime-riddled Quick Stop for a few months. His talk is easy because he’s packing.