A strange case of online harassment, complete with the usual police who would do nothing, may finally be coming to a close. A Montreal citizen who went by the online handle of Dave Mabus has been targeting the atheist and skeptic communities with threats and harassment for years. But Mabus' ability to target his threat was pretty limited (he often went after scientific journalists, including me), and that proved to be his downfall. Some clever Twitter users managed to redirect his rage-filled missives, first to a journalist in his home town of Montreal, and ultimately to the Montreal police department.

The person who goes by the name of Dave Mabus has apparently been at this for a while, as noted atheist PZ Myers claims to have been getting material from him for nearly two decades. Apparently inspired by fervent beliefs in both religion and the prophecies of Nostradamus, Mabus was incensed by the mere existence of atheists and skeptics who raised questions about them, such as Richard Dawkins, James Randi, and Michael Shermer. Starting with e-mail and newsgroups, Mabus sent off angry and vulgar rants to an ever-widening circle of targets. He also moved with the times, adding additional media for his anger: Web discussion boards, various blogs he opened and, eventually, Twitter.

Whatever else this behavior said about his mental state, Mabus did demonstrate impressive patience. As soon as one e-mail service or blog host closed off an account due to complaints of harassment, another would be opened. Evidence from various IP address traces showed he often connected via public computers or open WiFi hotspots scattered around Montreal.

Over time, he broadened his target list to the point of carelessness. "I don't think I ever said anything that directly set him off, in that I am not part of the atheist/skeptic community, which seemed to be his main targets," science writer Maryn McKenna told Ars. "I assume I was just collateral damage for being on the same RT strings as others he was more interested in."

I had largely the same experience, as did writer Carl Zimmer, who shared an archive of some of the e-mails he's received from Mabus over the years.

Many of these were simply vulgar rants against anyone who promoted atheism or questioned Nostradamus. But there are a number that clearly imply a threat: "Kicking in the heads of atheists one at a time...," "now we are going to bury you...," "we're this far from nuking all of you...." But many of the recipients also reported obvious threats to themselves and their families. More worrying still, the Atheist Alliance International held its convention in Montreal in 2010, a move that sparked this response from Mabus, found in one of Zimmer's e-mails: "NEW GAME WITH YOU LITTLE F*CKERS - SPEAK N DIE." And then, reportedly, Mabus' real-life counterpart did show up at the meeting.

Many others have suggested Mabus' imagery grew increasingly unnerving. "Whether he would ever get violent, I don't know," Zimmer said. "But he was a disturbing figure in many people's lives."

Behind the pseudonym

Despite his frequent use of anonymous services and public access points, Mabus apparently wasn't all that careful about concealing his identity, which is how people could tell that he had had shown up to the convention. Several of the e-mails he sent included a name in the return address: Dennis Markuze. IP addresses led to Montreal, and checks of the Montreal phone directory revealed there were only a few numbers listed with that last name. With his targets getting increasingly worried about the threats they were receiving, people started filing complaints with various law enforcement agencies, including the Montreal Police.

And, as far as anyone could tell, the complaints went nowhere. The local authorities weren't interested in acting, and most of Mabus' targets didn't even live in Canada. That eventually changed, in part due to Mabus' lack of discretion when it came to choosing his targets. One of Zimmer's tweets apparently caught the attention of William Raillant-Clark, who handles press for the University of Montreal. Calling the inaction "unacceptable," Ralliant-Clark began investigating the story and placed his results on Tumblr; he also included the Montreal Police's press account on Twitter in some of the conversation.

Here's where Mabus' thoroughness backfired. Noticing the Twitter conversation between Ralliant-Clark and his former victims, he added the journalist to his target list. And, since the Montreal police's Twitter account was also mentioned, it got a copy too. Mabus actually started sending diatribes to the local police force.

At the same time, someone named Kyle VanderBeek also became a target of Mabus' attack. The organization he works for, change.org, has an online petition system. VanderBeek set one up that asked the Montreal police to end the harassment; the system sent an e-mail to the police with each signature. By this time last week, the Montreal police had launched an investigation and were asking for the e-mails to stop, while Ralliant-Clark was being interviewed on TV. Later that evening, the latest Mabus Twitter account started issuing apologies.

By Tuesday, the police announced that they had arrested a suspect in this case. The Canadian judicial system will now decide whether his frequent threats require some sort of formal intervention.

Unfortunately, it took years of abuse and threats before anything was done; in the meantime, a larger number of people have been targeted by his threats, wasted time blocking his screeds, or had their conversations disrupted by his rants. The only consolation is that the same personality trait that allowed him to be disruptive—his indifference to the targets of his harassment—finally led him to target the Montreal police.