A man accused of carrying out Japan's worst mass killing since the end of the Second World War appeared to be smiling as he was transferred from police custody to see prosecutors.

Satoshi Uematsu, 26, a former employee at the care centre where he is suspected of murdering 19 residents, looked relaxed as cameras surrounded the police van.

According to Japanese media he has been co-operating with investigators and answering their questions clearly.

Shortly after the attack in Sagamihara he reportedly walked into a police station and told officers: "I did it.

"I want to get rid of the disabled from this world."


He is since said to have detailed how he tied up members of staff up with plastic ties, and deliberately targeted people with such severe disabilities that they were unable to communicate.

Cable ties and a number of knives were found in his car.

Images showed the steering wheel stained with blood.

The facility cared for people with a wide range of disabilities - both for short term respite and long term residential care for those with the most severe disabilities.

The attack took place in the early hours of the morning, when residents would have been asleep.

Many are reported to have had their throats slit.

Nine women and 10 men were killed, while 26 were injured, many of them seriously. The youngest victim was 18 years old, the oldest was 70.

Image: The attack took place at a care centre in Sagamihara

Five months before the attack, Uematsu sent a letter addressed to the speaker of Japan's lower house of parliament, in which he called for euthanasia for people with severe disabilities.

"I am fully aware this is a statement that defies common sense," he said, according to a copy of the letter obtained by the Kyodo news agency.

"However, I could not stand idle as I thought about the exhausted look on the faces of their caretakers, the crazed look in the eyes of the staff working at the facilities, and, in the best interest of Japan and the world, I have been moved to take this action today."

He said he could "obliterate" 470 people by targeting facilities at night, when the number of staff on duty would be lower.

"My goal is a world in which the severely disabled can be euthanised, with their guardians' consent, if they are unable to live at home and be active in society."

He promised to carry out the killings without harming staff, and said he hoped to be found "not guilty by reason of insanity."

Tokyo police notified their counterparts in the local prefecture and shortly afterwards Uematsu voluntarily resigned from his job at the care home and was "involuntarily" treated for psychiatric evaluation.

Tests showed he used marijuana and suffered from paranoia, but after 12 days he was discharged.

Yuji Kuroiwa, the governor of Kanagawa prefecture, said he had been told Uematsu suddenly changed before his resignation in February.

"Nothing much happened during the five months after he left his job," Kuroiwa said.

"You could say there were warning signs, but it's difficult to say if this could have been prevented."

Neighbours described Uematsu as an outwardly polite and kind young man.

Akihiro Hasegawa, who lived next door to him for eight years, said: "He always smiled when he greeted me."

"He was very mannerly and polite. A really nice young man."

Around the time of the attack, a Twitter account in Uematsu's name posted a photo of a man in a red tie, shirt and jacket with the message: "I hope for world peace. Beautiful Japan."