So, just kill all? No declaration of borders or warnings to people? Not strong enough to announce their sovereignity or just can't be bothered to think about it... yes, they want to "hide" but if enough people just keep getting killed eventually... well.
How poetic would it be if this jackass got his ass handed to him if an S-rank party showed up due to all these "disappearances". Won't happen though, since he's the MC. He'll probably pull out a trump card out his ass without any context as to him ever having said trump card. Would be nice for him to eat dirt though...