I’m linking to the Asahi Shinbun’s coverage rather than the more “excitable” story I first saw from The Daily Mail. Short version: a former employee at a home for the disabled went in with a knife and killed at least 19 patients, wounding many more. There’s already a Wikipedia page linking to random news stories about it, which strikes me as rather voyeuristic.
[Update: five months ago, he sent a polite letter to the government announcing his detailed plans and asking for official support. It’s not clear from the stories whether he wrote the letter and then got fired when the police investigated, or got fired first.]