A knife-wielding man who killed two people Sunday night in a south China Walmart outlet is unemployed and conducted the attack alone, police said.

The 30-year-old suspect, surnamed Jiang, has been detained after attacking people with a kitchen knife in Bao'an District, Shenzhen City, at around 9 p.m., Shenzhen police said. Nine people are receiving treatment after sustaining injuries.

According to Jiang's family, he hails from the southwestern municipality of Chongqing and became a migrant worker in 2014. The family posted a notice inquiring about Jiang's whereabouts in September 2015 after he lost contact with the family.

In the notice, the family claimed Jiang has a mental illness.

According to Shenzhen police, Jiang was clear-minded when he was questioned. A medical evaluation will be conducted to confirm his mental state.