A knife-wielding man killed two people and wounded nine others in a supermarket in southern Chinese city of Shenzhen, Guangdong Province, on Sunday night, local authorities said.
The attacker was detained and the wounded have been sent to the hospital.
Police said the 30-year-old suspect, surnamed Jiang, is unemployed and acted alone.
Jiang's family claimed he has been suffering from a mental illness, but police said he was clear-minded when questioned. A medical evaluation will be conducted to confirm his mental state.