Police have detained a man they suspect of killing a school principal and critically injuring a student on Tuesday in Xinhua county in the city of Loudi, Hunan province.

Wang Zhichu, 27, is believed to have sneaked into Beidu primary school by jumping over the school's fence at about 1:50 pm on Tuesday. Police say he approached Wang Zhenyu, a 9-year-old third-grader, and stabbed him in the head with a pair of scissors.

Kang Guimei (left), wife of Yang Jianyi, is overcome with grief as she learns of the death of her husband on Tuesday. [Guo Guoquan/ For China Daily]

School principal Yang Jianyi, 59, tried to stop the attack and was stabbed to death in the ensuing struggle.

The suspect is unemployed and has a history of mental illness. Police detained him on Tuesday evening and Wang Zhichu confessed the next day that he had attacked the pupil and stabbed the school principal to death, police in Xinhua county said.

The student suffered wounds as deep as five centimeters to his skull, China Central Television reported on Wednesday. He underwent two operations on Tuesday night and is now in the intensive care unit of a Loudi hospital. Doctors said he is in critical condition and may not survive.

Upon hearing of the attack, the 28-year-old son and 25-year-old daughter of the deceased principal rushed back from Shenzhen, Guangzhou province, where they are migrant workers.

A memorial service for their father will be held at 10 am on Thursday.

More than 300 villagers gathered to pay tribute to Yang when his body was moved from the crime scene to a funeral home on Tuesday afternoon.

"I hope I can keep my mother at home when the memorial service happens," said the principal's son Yang Hongwei. He said his mother, Kang Guimei, was in deep mourning and refused to eat or drink anything.

"I don't feel angry," Yang said. "But a good person like my father shouldn't be killed in this way."

Yang said he remembered his father as being a loving parent and devoted teacher who spoke little but accomplished much.

Yang said he believed his family will see justice and the attacker will be duly punished for his crime.

Top Xinhua county officials went to the school immediately after the tragedy.

At a meeting in the county on Wednesday afternoon, public servants were called on to honor the principal's heroic deeds and donate money to his family.

Officials from the county's campus safety office have spoken with teachers and students who witnessed the violence and are trying to help them cope with the trauma the attack subjected them to.

Wang Liuyin, a lawyer from the county judicial bureau's legal assistance center, said the trial and eventual sentencing of the suspect will take place after experts provide a detailed evaluation of his mental state.

Wang Liuyin said she has heard in recent years of more and more crimes involving mentally ill suspects.

She said it would be impossible to establish a database holding records of everyone's mental health status. She said the illnesses are often discovered only after the people who have them commit serious offences.

Guo Guoquan contributed to the story.

liyao@chinadaily.com.cn