The head of a school in Japan whose pupils were targeted in a deadly mass stabbing on Tuesday has said he is “heartbroken” by the attack, which left two people dead and 17 others injured.

Most of those injured were pupils at Caritas Gakuen primary school in Kawasaki, near Tokyo.

Teachers at the school described one of the victims, 11-year-old Hanako Kuribayashi, as “thoughtful and good-natured”, while neighbours said they often saw her and her mother walking the dog.

Her father asked the media to give the family time to grieve. “Please spare us today,” he told reporters outside his home, according to Kyodo news agency. “We’ll respond eventually, but I can’t leave my wife alone today.”

Tetsuro Saito, head of Caritas Gakuen school group, left, and Teiko Naito, head of Caritas Gakuen elementary, at a news conference on Tuesday. Photograph: Issei Kato/Reuters

Tetsuro Saito, the school’s director, said: “My heart is broken with pain when I think of the innocent children and their parents, who send their children to our school with love, but who were the victims of this savage act. I’m struggling to control my anger.”

The second victim, Satoshi Oyama, a 39-year-old foreign ministry official who was seeing his daughter off to school, died in hospital from stab wounds to his neck and back following the attack.

Oyama, whose daughter was unharmed, worked on the ministry’s Myanmar desk and had interpreted for the country’s leader, Aung San Suu Kyi, when she visited Japan in 2013, according to public broadcaster NHK.

Media quoted police as saying that Oyama may have sustained stab wounds to his back while trying to protect the children.

Kawasaki stabbing victim Satoshi Oyama in an image released by the Japanese foreign ministry. Photograph: Japanese foreign ministry

Japan’s former ambassador to Myanmar, Tateshi Higuchi, said he had been shaken by news of Oyama’s death, describing him as “warm-hearted, humble and genuine”, according to Kyodo.

According to the foreign ministry, Oyama, a graduate of Tokyo University of Foreign Studies, joined the ministry in 2004 and spent five years working at the Japanese embassy in Yangon.

The attacker, identified as Ryuichi Iwasaki, a 51-year-old resident of Kawasaki, reportedly lived with his elderly aunt and uncle and was known as a troublemaker.

The Sankei Shimbun quoted a neighbour as saying that Iwasaki had repeatedly rung her doorbell early one morning last summer and complained loudly to her husband that he had been struck in the eye by an overhanging tree branch outside the couple’s house.

Armed with a knife in each hand, Iwasaki reportedly crept up on the pupils as they were boarding a bus to school.

Eyewitnesses said he shouted that he was “going to kill” the children as he launched the attack.

But Satoru Shitori, the headmaster of Caritas Gakuen’s primary school, said no one noticed Iwasaki approach the bus stop. “He did not speak, cry out or shout,” he said. “He did not say a word. That’s why children didn’t notice. If he had been shouting, the children might have been able to escape.”

Iwasaki reportedly stabbed himself in the neck after being pursued by the bus driver and died in hospital from his injuries.

The prime minister, Shinzo Abe, said the government would take measures to ensure children’s safety while traveling to and from school.

While the attack was one of several mass stabbings in Japan in the past two decades, the country is regarded as one of the safest in the world. It is not unusual for even young children to travel alone to school on public transport.