SAGAMIHARA, Japan — A mass stabbing at a center for people with disabilities outside Tokyo on Tuesday shocked Japan, where violent crimes are extremely rare.

A former employee who had expressed strong views about euthanizing disabled people returned to the center with a bag of knives at around 2 a.m., methodically slitting the throats of patients as they slept.

When he left the building 30 minutes later, 19 people were dead in the worst mass killing in Japan since World War II. The dead ranged in age from 19 to 70. Twenty-six people were wounded, 13 of them critically.

The suspect, Satoshi Uematsu, 26, who had sent a letter to a politician five months ago outlining his plan, calmly turned himself in at a nearby police station a half-hour after the attacks. As he confessed, he told the authorities, “All the handicapped should disappear.”