A man who set off a self-made explosive device outside a nursery in eastern China had a neurological disorder and had scrawled words including “death” and “terminate” on the walls of his home.
Eight people, including children, were killed and 65 others injured in the blast.
In a briefing shown on state TV, police said the man, who also died, was 22 years old. His surname was Xu.
The blast happened outside the gates of the Chuangxin Kindergarten in Xuzhou on Thursday.
The People’s Daily said that contrary to earlier reports, it did not happen while parents were picking up their children after school.
Two victims died at the scene of the explosion in the coastal province of Jiangsu, while six more died in hospital.
Eight people were in a critical condition, the official Xinhua news agency said on Thursday night.
China Central Television said Xu had dropped out of school because of his condition and rented a flat near the nursery.
“Self-made explosive device materials were found in his apartment, and on the walls in many places were handwritten words such as kill, death, destroy and terminate,” it reported.
Graphic images on social media purportedly showed the scene with adults and children lying on the ground.
Public security minister Guo Shengkun ordered a prompt investigation and “demanded enhanced checks of possible risks at densely populated venues”, Xinhua said.
His deputy was sent to the area to conduct the probe.
A statement was issued by China’s education ministry demanding that security be strengthened around schools to ensure teachers’ and pupils’ safety.
The blast is the latest tragedy to strike nursery schools in China in recent months.
In May, 11 children were killed along with their teacher and driver when their school bus caught fire inside a tunnel in eastern Shandong province.
Officials later said the fire was started by the driver who was angry about losing overtime wages.
In January, a man armed with a kitchen knife stabbed and wounded 11 children at a nursery school in the southern region of Guangxi Zhuang.