A prominent Japanese blogger who was an expert on the “dark web” was stabbed to death shortly after giving a talk about internet trolls.
The blogger, Kenichiro Okamoto, 41, was killed on Sunday at a business incubator in Fukuoka City, about 550 miles west of Tokyo, the Japanese newspaper Asahi Shimbun reported, citing unnamed police officials.
The police arrested Hidemitsu Matsumoto, a 42-year-old man in connection with the killing.
The two men had not met in person. But Mr. Matsumoto had harassed Mr. Okamoto with online messages and “held a grudge” against Mr. Okamoto, according to the newspaper, and Mr. Okamoto had tried to block Mr. Matsumoto’s messages.
“I thought I would kill him,” the newspaper quoted Mr. Matsumoto as telling the police.
Mr. Okamoto, who wrote under the pseudonym “Hagex,” was a popular blogger with more than 26,000 posts that reached 1,060 followers. He embedded online comments from other websites and added short commentaries.
He worked at an information security firm in Tokyo and was frequently consulted by journalists as an authority on internet security.
Shortly after Mr. Okamoto finished his lecture at about 8 p.m., Mr. Matsumoto attacked the blogger. He stabbed him in the neck and chest multiple times inside a men’s restroom in the former elementary school, the newspaper reported.
The suspect fled on a bicycle but then turned himself in within a few hours, according to the newspaper. In the meantime, an anonymous user — possibly Mr. Matsuomoto himself — posted online that the suspect was “now going to surrender himself to take responsibility.”
In a blog entry posted on May 2, Mr. Okamoto discussed an internet troll he dubbed “Mr. Low I.Q.” The troll, he wrote, repeatedly posted slander on the internet and harassed him seven times in a single day. The police were not immediately able to confirm that the troll in question was Mr. Matsumoto.
Mr. Okamoto had served as an editor of a cybersecurity magazine before landing his position at a company that provides consulting to other companies and government agencies on cybersecurity and conducts research on so-called “dark web,” according to Sprout, the cybersecurity company where Mr. Okamoto worked.
The dark web is a part of the internet that requires an encrypted network and specialized tools that grant anonymity. Criminals have often exploited it for illicit activities and hate-mongering.
“Losing Mr. Okamoto has been a matter for deep regret for the company,” Seigen Takano, the chief executive of Sprout, wrote on its website. “It can’t help saying that we’ve lost a person who was valuable for the future of the cybersecurity industry.”