On February 6, an anonymous message appeared on a Japanese bulletin board, predicting a random attack. Memories of the Akihabara Massacre came flooding back, and the police moved into action.
"On February 11, at 9pm sharp, there will be random slashing at Shinjuku Station's highway bus entrance," the message read. "You might want to sit this round out if you don't want to die."
On the bulletin board, the attacker apparently wrote that three individuals will carry out the attack: one in a car, and two brandishing knives.
Eighty Tokyo Metropolitan police officers were assembled and around 500 people from online looked on to see what havoc would break out. The police began tracking the IP address used to make the message. But it wasn't just any IP address, it was an IP address specific for a game portable — a Nintendo DSi.
At around four in the afternoon on February 11, hours before the attacks were apparently going to start, the IP address was traced to an electronics store in Kawasaki City, and a teenage boy, a 15-year-old junior high student from Yokohama, was discovered using a Nintendo DSi.
The 15-year-old was arrested, telling the police, "I acted alone. I just wanted to see how much chaos it would cause." A late night bus pass to Osaka was discovered in his possession, making it possible he planned to escape to Western Japan.
威力業務妨害：ネットに通り魔予告 中３少年逮捕…警視庁 [毎日ｊｐ(毎日新聞)]