I own and operate a community that specializes in radio communications technologies, and I've actually had an instance of a member who we banned who threatened me personally and my family by trawling through property tax records to find out personal info, photoshopped pictures of my family, and registered tons of accounts through proxies and VPNs to harass our staff and moderators. Because of the detailed, targeted threats (like specifically threatening my wife and children by name) I went to the police. They ended up simply calling him on the phone to try to get to the bottom of the entire saga and he strongly apologized (through the police, they told him to not even think about contacting me). It was as if he finally realized the severity of his actions, only when law enforcement got involved. But it was actually pretty scary because of the targeted detailed aspects of how he exacted retribution.
I think the vast majority of these types of issues are mental health related. But it seems like an especially acute problem for niche businesses and communities. The time and effort it caused me to exert made me so upset that I would have cheered a 26 month prison sentence just to make an example out of the guy, but law enforcement encouraged me to just move on.