Please view the main text area of the page by skipping the main menu.

Man arrested for allegedly fatally stabbing 'dark web' cyber security worker in Fukuoka

Police investigate near the site of murder in Fukuoka's Chuo Ward, on June 24, 2018. (Mainichi)

FUKUOKA -- A man was arrested here on suspicion of fatally stabbing an IT security consulting firm employee knowledgeable about cybercrimes including those involving so-called "dark" websites, the Fukuoka Prefectural Police announced on June 25.

The victim, 41-year-old internet security firm employee Kenichiro Okamoto of Tokyo's Koto Ward, was giving a lecture at a facility inside the now-defunct Daimyo Elementary School, in Fukuoka's Chuo Ward, on June 24. At around 8 p.m., a man linked to the facility called police to report a stabbing. Okamoto was found with multiple stab wounds to his chest and neck from a knife with a roughly 16.5-centimeter blade, and was rushed to the hospital where he was confirmed dead.

According to the Fukuoka Prefecture Police, at around 10:50 p.m. on the same evening, a man in his 40s visited a police box under the Higashi Police Station and turned himself in, saying, "I am responsible for the murder in Chuo Ward." A bloody knife was found inside the man's bag, and police arrested 42-year-old Hidemitsu Matsumoto of Fukuoka's Higashi Ward on June 25 on suspicion of violating the Act for Controlling the Possession of Firearms or Swords and Other Such Weapons and the murder of Okamoto.

According to the webpage of his employer, a cyber-security consulting company in Tokyo, Okamoto was knowledgeable about cybercrimes such as those involving so-called "dark" websites, part of the internet that cannot be accessed without special software to make one anonymous. He was also famous for a blog that he wrote under the nickname "hagex." According to a related source, Okamoto "had gotten into trouble before with internet users over the content of the blog."

Police quoted Matsumoto as saying that he built up resentment toward Okamoto over some exchanges through internet posts and wanted to kill him. Immediately after the stabbing, a user that appears to be the suspect wrote on the web about his dissatisfaction toward the response to his own posts thus far, along with writing, "I am going to go now to my neighborhood police box to voluntarily surrender and take responsibility for my actions." The suspect has reportedly admitted to the charges against him.

Okamoto was attacked roughly 15 minutes after the seminar ended. Police say Matsumoto gathered information about the seminar ahead of time, and entered the facility without participating in the seminar. It appears that he attacked Okamoto in the restroom immediately following his lecture.

The man who called police reportedly heard a cry, "Call an ambulance!" from the first-floor restroom. When he ran to check, Matsumoto, holding the knife, and the stabbed Okamoto came out of the restroom. The suspect then allegedly fled on a bicycle. After he turned himself in, the footprints in the facility were matched to the suspect's, and a man resembling Matsumoto was caught on facility security cameras, leading to his arrest.

The location of the IT seminar was a facility to aid entrepreneurs, on the west side of the Tenjin district in the center of Fukuoka, in an entertainment district around 300 meters west of Nishitetsu Fukuoka (Tenjin) Station. When the incident occurred on Sunday evening, there were many people out in the area, and investigators gathered to push back the crowds to close off the crime scene.

"I was about to go into a restaurant inside of the facility when I heard someone running," said a 20-year-old man who was at the scene. "When I turned around, I saw a man had collapsed. There was a puddle of blood, and someone nearby yelled, 'Call an ambulance.' I thought it might be a street slasher, so I ran into the restaurant."

A 19-year-old attending a cram school also in the area said, "I was about to leave the school when I was told I couldn't. I always walk by there on my way to school, so it's really chilling when I think that there could have been a criminal like that nearby."

(Japanese original Kazuya Shimura, Nao Ishii, Takashi Miyazaki, Kenta Miyahara, Makoto Kakizaki and Yuta Hiratsuka, Fukuoka News Department)

Also in The Mainichi

The Mainichi on social media