A knife-wielding man went on a rampage early Tuesday at a care facility for people with disabilities in Sagamihara, Kanagawa Prefecture, killing at least 19 people and wounding 25 others, 20 of them seriously, in one of the worst mass killings in modern Japanese history.

The Kanagawa Prefectural Police arrested Satoshi Uematsu, 26, after he drove to Tsukui Police Station and turned himself in at around 3 a.m. Tuesday, about 15 minutes after staff at the Tsukui Yamayuri En (Tsukui Lily Garden) facility had called police.

Police quoted him as saying, “I did it.”

“It’s better that the disabled disappear,” the police further quoted him as saying. Uematsu was also quoted by the police as saying, “There is no question I stabbed people who could not communicate well.”

The police said Uematsu, a former employee of the facility and a resident of Sagamihara, showed up at the station with three bloodstained knives in a bag.

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The police initially arrested Uematsu, who is currently unemployed, on suspicion of attempted murder and unlawful entry.

They were seeking to determine the motive for the attack, though it emerged Uematsu had been committed to a mental hospital after he made threats to kill people with disabilities earlier this year.

Authorities said those killed comprised 10 women and nine men aged between 19 and 70.

Uematsu is believed to have broken into the facility at around 2:30 a.m. by smashing a first-floor window, investigative sources said. A hammer was found nearby.

They said he may have tied up some residents and staff as he went on the rampage.

Eight staff members and one security guard were on duty at the time.

Prime Minister Shinzo Abe said the government will do its utmost to get to the bottom of the incident, while Chief Cabinet Secretary Yoshihide Suga described the stabbing rampage as “highly distressing.”

Earlier in the day, Kanagawa Gov. Yuji Kuroiwa offered “sincere condolences and an apology” to the victims and their families.

The Kanagawa Prefectural Government, which administers the care facility, will do whatever it can to support the families and come up with measures to prevent a recurrence, Kuroiwa said.

A Kanagawa prefectural official said Uematsu worked at the facility from December 2012 to February this year.

On Feb. 14 and 15, he took a handwritten letter to the official residence of the speaker of the Lower House, in which he suggested he was planning to kill people at Tsukui Yamayuri En at night when the facility had fewer staff on site, according to the police.

“I dream of a world where the disabled can die in peace,” Uematsu wrote in the letter. “I will carry out the plan without hurting the staffers, and I will turn myself in after I kill the disabled.”

The letter also said he felt “sorry” for people with disabilities, many of whom were bound to wheelchairs for life. He further wrote that many of them had no contact with their family members.

Uematsu had also been questioned by police on Feb. 19 for telling workers at the facility a day earlier that he would “kill the disabled,” according to Sagamihara officials.

Uematsu was hospitalized after that until March on the grounds that he was a danger to others. At the same time, he quit his job. Traces of marijuana were detected in his urine when he was tested at the hospital, police said.

While his neighbors described him as a courteous and helpful man, he also been accused of breaking the law.

Police referred a case against him to prosecutors last December on suspicion of assault in a quarrel with a pedestrian in front of JR Hachioji Station, according to a Metropolitan Police Department official.

According to its website, the residential care facility for people primarily with intellectual disabilities was set up by the prefectural government and run by a social welfare corporation. It has about 30,000 sq. meters of total area and can accommodate up to 160 people.

As of the end of April, it had 149 residents between the ages of 19 and 75, with 40 of them believed to be over 60. All of the residents are classified between levels 4 and 6 in terms of the care they require, with 115 classified at level 6, the highest on the Health, Labor and Welfare Ministry-designated scale.

The facility is located about 50 km from central Tokyo near private residences and an elementary school.

After news about the stabbing rampage spread, families of the residents as well as neighbors flocked to the scene to get information about the residents’ condition, saying they had received no information from the facility.

“I called the facility and they said my son was hurt. But I can’t get in there and I have no idea what’s going on,” said a man in his 80s whose son, in his 50s, was living at the facility.

Hospitals in the vicinity rushed to treat the injured, some of whom were covered in blood and moaning in pain.

Kitasato University Hospital in Sagamihara, which admitted 13 of the injured, said that eight had suffered serious neck injuries.

Tokyo Medical University Hachioji Medical Center said all four of the injured it admitted were unconscious and covered in blood.

“We are conducting emergency operations and blood transfusions. We want to save them,” said Takao Arai, head of the center. “I have an impression that the perpetrator was deliberately targeting necks. I suspect he had strong intentions to kill.”

The early morning attack was one of the worst single-perpetrator mass murders in postwar Japan.

In 2001, a man entered an elementary school in Ikeda, Osaka Prefecture, stabbed eight children to death and wounded 15 other people.

In 2008, a man rammed a truck into a street crowd in Tokyo’s Akihabara district, running people over and then going on a stabbing spree. The indiscriminate attack killed seven and injured 10.

In 2010, a man set an adult video-viewing shop on fire in the Nanba district in the city of Osaka, killing 16.