WEARING a casual striped T-shirt and grinning from ear to ear the young man doesn’t look like he has a care in the world.

But just hours earlier, Satoshi Uematsu, 26, is alleged to have brutally killed 19 people in a Tokyo care facility and injured a further 26 others.

A picture emerged on Wednesday of the man being blamed for the country’s worst mass killing in decades.

But far from showing remorse for his actions or regret for the heartache he’s caused, Uematsu looked happy and relaxed. Bent over in the back of a police car, his distinctive blond hair tumbling across his forehead, he smiled warmly at the media throng outside.

Uematsu was transferred on Wednesday morning from a local police station in the city of Sagamihara, 50km west of Tokyo, to the prosecutor’s office in Yokohama.

His head and shoulders covered with a blue jacket, he was led out of a police station and into the back of an unmarked white van with emergency lights on top.

Uematsu had been held at the police station all day and overnight after turning himself in about two hours after Tuesday’s pre-dawn attack.

Police also searched the man’s house in the same city.

Kanagawa prefectural authorities said Uematsu had left dead or injured nearly a third of the almost 150 disabled patients at the facility in a matter of 40 minutes.

In a chilling letter, penned in February, the suspect had called for the “euthanasia” of disabled people and said he would be willing to carry out the acts himself if needed.

Uematsu boasted in the letter that he had the ability to kill 470 disabled people in what he called was “a revolution”, and outlined an attack on two facilities, after which he said he would turn himself in. He also asked he be judged innocent on grounds of insanity, be given 500 million yen ($5 million) in aid and plastic surgery so he could lead a normal life afterwards.

“My reasoning is that I may be able to revitalise the world economy and I thought it may be possible to prevent World War III,” the letter said.

After the letter was intercepted, Uematsu was “hospitalised” by officials in the Kanagawa prefecture.

Police said they responded to a call about 2.30am on Tuesday morning from an employee saying something horrible was happening at the facility.

Uematsu allegedly entered the building about 2.10am by breaking a glass window on the first floor of a residential building at the facility, a health official told reporters at a news conference.

He then set about slashing the patients’ throats. The youngest victim was 19, the oldest 70.

About two hours later a man turned himself in at a police station, police in Sagamihara said.

Uematsu had worked at the facility until February.

Japanese broadcaster NTV reported that Uematsu was upset because he had been fired, but that could not be independently confirmed.

The facility, called the Tsukui Yamayuri-en, was home to about 150 adult residents who have mental disabilities, Japan’s Kyodo News service said.

Details of the attack, including whether the victims were asleep or otherwise helpless, were not immediately known. Kanagawa prefecture welfare division official Tatsuhisa Hirosue said many details weren’t clear.

Uematsu had worked at Tsukui Yamayuri-en, which means mountain lily garden, from 2012 until February, when he was let go. He knew the staffing would be down to just a handful in the early hours of the morning, Japanese media reports said.

The facility employs more than 200 people, including part-timers, with nine of them working the night of the attack, Hirosue said. All those killed were patients.

“They were working at night and were questioned by police after witnessing graphic violence, making them a little emotionally unstable now,” he said.

Some people in the area said they were shocked that Uematsu was accused, and described him as polite and upstanding.

Akihiro Hasegawa, who lived next door to Uematsu, said he heard the man had got into trouble with the facility, initially over sporting a tattoo, often frowned upon in mainstream Japanese society because of its association with criminal groups.

“He was just an ordinary young fellow,” he said.

Mass killings are rare in Japan. Because of the country’s extremely strict gun-control laws, any attacker usually resorts to stabbing. In 2008, seven people were killed by a man who slammed a truck into a crowd of people in central Tokyo’s Akihabara electronics district and then stabbed passers-by.

In 2001, a man killed eight children and injured 13 others in a knife attack at an elementary school in the city of Osaka. The incident shocked Japan and led to increased security at schools. This month, a man stabbed four people at a library in northeastern Japan, allegedly over their mishandling of his questions. No one was killed.