These gangs are neither Islamic scholars nor leaders of the community. They have no authority to go around with their self styled namesake "shariah" implemented by dubious means that come down to nothing but la madhabi ramblings of the modern day khawarij. The khawarij of the past used to in a similar way go to weak powerless villages and impose their pseudo shariah and pseudo jihadi programmes. They also put takfir on people because of the absence of a general forbiddence of evil by the community.