Police have served another arrest warrant on the alleged perpetrator of the deadly knife rampage at a care facility for people with disabilities last month in which 19 were killed and 27 injured.

This warrant on Satoshi Uematsu, 26, deals with the slayings of nine female residents of the facility in Sagamihara, Kanagawa Prefecture. The police said he has admitted to the allegations.

Uematsu was initially arrested July 26, the same day that he turned himself in at a local police station for allegedly breaking into the Tsukui Yamayuri En facility and fatally stabbing a 19-year-old woman there.

Uematsu is suspected of stabbing residents with knives in the early hours of July 26 after entering the facility by breaking a window with a hammer on the ground floor and tying up staff members.

Investigative sources said the incident was premeditated as Uematsu had brought a letter to the official residence of the speaker of the Lower House speaker in February stating, "My goal is creating a world in which euthanasia can be used on people with multiple disabilities." The letter identified the Sagamihara facility as one of his targets.

When Uematsu turned himself in, he was carrying a bag containing three blood-covered knives, a hammer and zip ties. Two other knives were found at the facility.

Investigators plan to serve another arrest warrant on him over the remaining nine male victims while also pursuing charges over the injuries inflicted on the victims who were not killed, the sources said.