A man armed with a knife killed eight boys and wounded four others at a high school dormitory in the city of Ruzhou, in central China, reported China's Xinhua news agency Friday.
State media report that a mother reported her 21-year-old son, Yan Yanming, to police after he tried to commit suicide following the attack.
The attack at the No. 2 High School took place around 11:45 p.m. Thursday.
"The man broke into the high school with a knife in his hand...and chopped eight people to death and four others to injury," said the Xinhua report.
There's no word on the attacker's motive, though the China News Service says he might have been a former student who may have been expelled.
There have been several knife attacks in Chinese schools and day-care centres in the past few months.
Those attacks led the government to demand schools hire guards and tighten security around schools.
A man who slashed 25 children at a grade school in eastern China in September was executed for his crime on Wednesday.