TOKYO » The killing of 19 people at a home for the mentally disabled raised questions about whether Japan’s reputation as one of the safest countries in the world is creating a false sense of security.

The deadliest mass killing in Japan in the post-World War II era unfolded early Tuesday in Sagamihara, a city about 30 miles west of central Tokyo, when authorities say a former employee broke into the facility and stabbed more than 40 people before calmly turning himself in to police.

The suspect, identified as 26-year-old Satoshi Uematsu, had worked at the facility from 2014 until February, when he was let go. He wrote to Parliament outlining the bloody plan and saying all disabled should be put to death.

While not immune to violent crime, Japan has a relatively low homicide rate of well under one per 100,000 people. Mass killings usually are seen half a world away on the nightly news, although seven Japanese were among the dead in a recent hostage-taking in Bangladesh that targeted non-Muslims.

Because such massacres are rare, Japan has become overconfident about its safety, a Japanese criminologist said.

For crime prevention, the country relies on its social system in which a group mentality sacrifices individual freedom for collective safety, said Nobuo Komiya, a criminology professor at Rissho University in Tokyo.

As a result, it has neglected risk management, he said.

“Japan has put an emphasis on not creating criminals, but it is reaching a breaking point,” Komiya said. “Like in foreign countries, I think institutions need to develop a plan in operational management and prepare for a worst-case scenario, given that criminals are inevitably born.”

Mass killings have happened in Japan from time to time. In 2001, a man with a history of mental illness killed eight children in a knife attack at an elementary school in Osaka. The attack prompted increased security measures for schools. In 2008, a man rammed a rented two-ton truck into a crowd of shoppers at a busy Tokyo intersection, then jumped out and began stabbing people, killing seven.

Japan has very strict gun laws that might lessen violent crime, but they can’t stamp it out. TV news regularly reports on murders — a jilted lover, an adult son angry at his parents — and the most common weapon is a kitchen knife.

A Justice Ministry study in 2013 found that knives were used in slightly more than half the murder cases in a given year, with kitchen knives accounting for more than a third of all cases.

National Police Agency statistics show there have been fewer than 10 shooting deaths annually in Japan in recent years, a number that dropped to just one case in 2015.

The comfort level is high enough in Japan that it is common practice for first-grade students to go to and from school on their own, after parents accompany them for the first month or so, even in a major city such as Tokyo. Children are kidnapped from time to time.

Another factor contributing to Japan’s sense of safety, Komiya said, is the fact that the island country has never been invaded.

Tuesday’s attack prompted at least two major newspapers to publish “extra” editions that were handed out at train stations as details emerged. All 19 dead were among the approximately 150 residents or short-term residents at the Tsukui Yamayuri-en home for the mentally disabled.

Of the nine workers who were at the facility, two were injured but none died, Kanagawa Prefecture official Tatsuhisa Hirosue said.

The attack shocked neighbors, many of whom said they had a good relationship with both the staff and the residents of the home in the hilly, semi-rural community in Sagamihara.

Reiko Kishi, an 80-year-old neighbor who worked at the home for more than 30 years, said he was awakened by the sirens of ambulances and other emergency vehicles coming one after another in the middle of the night.

“Such a crime is unheard of in this slow and peaceful suburban neighborhood,” she said. “I will be more careful about locking the door and windows, at least on the first floor.”

It’s a lesson that perhaps more of Japan will heed. Takeshi Koyanagi, a professor at the International Victimology Institute at Tokiwa University in Mito, warned of possible copycat attacks.

Associated Press reporter Mari Yamaguchi in Sagamihara, Japan, contributed to this story.