Japanese police have arrested a man suspected of being behind a computer hacking campaign following an exhaustive hunt that at one stage had authorities tracking down a cat for clues, reports said.
Yusuke Katayama, 30, was arrested on Sunday on charges of using a remote computer and sending a mass killing threat to a comic book event after months of evading investigators with a series of vexing cyber riddles, according to local news agency NHK.
The broadcaster aired footage of detectives escorting a chubby man with glasses into a police station.
Katayama is believed to have sent numerous threats from computers around the country, including against a school and a kindergarten attended by Emperor Akihito's grandchildren.
The National Police Agency (NPA) was embarrassed after it emerged that officers had extracted "confessions" from four people who had nothing to do with the threats.
An anonymous hacker then sent messages to newspapers and broadcasters last month, with the sender claiming details of a computer virus used to dispatch the threats were strapped to a cat living on an island near Tokyo.
After cracking a set of riddles, police found the cat and removed a digital memory card from its collar which revealed a message saying "a past experience in a criminal case" had caused the hacker to act.
The message said the case "changed" the anonymous hacker's life, and added that "no more messages will be sent", local media reported.
Police analysed the memory card and footage captured by security cameras, coming to suspect that Katayama, a Tokyo resident, was responsible for the hacking campaign, Jiji Press and other media said.