KAWASAKI, Japan — Every morning across Japan, parents say goodbye to their children and send them off to school. Students as young as 6, dressed in easily identifiable uniforms and shouldering boxy leather backpacks, travel to school on their own, their families secure in the knowledge that Japan is one of the safest countries in the world.

That peaceful assumption was shattered Tuesday morning when a man wielding two long-blade knives stabbed 17 schoolgirls and two adults at a bus stop in a suburb southwest of Tokyo, according to the police. One of the girls, an 11-year-old, and a 39-year-old man died in the assault, and the attacker fatally stabbed himself.

It was a shocking event for a country where violent crime is rare and the kinds of mass shootings that have devastated schools across the United States have never occurred because of strict gun-control laws.

By Tuesday night, the police had not identified a motive. Officials at Caritas, the Roman Catholic school in Kawasaki that the children attended, said they had received no warning and did not know the attacker, who was identified by NHK, the public broadcaster, as Ryuichi Iwasaki, 51.