The 26-year-old reportedly said he wanted all disabled people to "disappear" after the knife rampage that left his victims in pools of blood, including some who were stabbed in the neck.
With a blue jacket draped over his head, Satoshi Uematsu was escorted out of a police station into a waiting van before a crowd of flashing news cameras.
Inside the vehicle with the jacket removed, he smiled broadly in footage broadcast on morning news shows.
Uematsu is accused of breaking into the Tsukui Yamayuri-en care centre in the forested hills of Sagamihara city, outside of Tokyo, in the early hours of yesterday.
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He reportedly tied up two caregivers before stabbing residents, leaving a total of 26 people injured, 13 of them severely.
He quickly turned himself in at a police station, carrying bloodied knives and admitting to officers: "I did it".
He reportedly also said: "The disabled should all disappear."
At around 2:50 am, shortly after an emergency call was made to police from the centre, the footage shows the driver dashing back to the vehicle, carrying a large bag in his right hand.
Uematsu left his job at the care home and was forcibly hospitalised in February after telling colleagues he intended to kill disabled people at the centre.
But he was discharged 12 days later when a doctor deemed he was not a threat.