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A knife attack on a care centre for people with mental disabilities in Sagamihara, Japan

After breaking into the centre on 26 July the alleged attacker stabbed residents at random then drove to a local police station and confessed, saying he wanted disabled people to "disappear".

The killer has been named by police as Satoshi Uematsu, a 26-year-old former employee of the centre, Tsukui Yamayuri-en. It is not clear what role he worked in. Some reports suggest he was fired from the centre, but still lived nearby.

One local woman said she knew Mr Uematsu, and he had "a cheerful impression" and was "the kind of person that would greet you first".

But a darker picture emerged of him when police revealed that in February he had taken a handwritten letter to Japan's parliament saying he would kill 470 severely disabled people if authorised: "I want Japan to be a country where the disabled can be euthanised."

He was subsequently taken to hospital but released about two weeks later.

A Twitter account, believed to be one maintained by Mr Uematsu, on 13 February posted: "I don't know if it's right but I should act." It is not clear what he is referring to. A tweet on 19 February says he had been given "voluntary retirement" but that he "might be arrested anyway".

And then on Tuesday, a tweet posted shortly after the attack in the early hours of the morning showed a dark selfie and the words: "For world peace, beautiful Japan."