Thirty-five people were killed after a man drove a vehicle into a crowd at a sports center in the southern city of Zhuhai, Chinese police said Tuesday, in a rare case of deadly violence in a country where police surveillance is ubiquitous.

Another 43 people were injured in the crash Monday evening, the Zhuhai Municipal Public Security Bureau said. Authorities did not explain why the death toll, one of the country’s highest from a single incident in recent years, was released a day later.

President Xi Jinping of China on Tuesday night ordered local officials to ensure safety and social stability and “strictly prevent extreme cases,” according to state-run news reports. Within hours, other top Communist Party officials moved to reassure the public that authorities would bolster security.

Police detained the driver, who was identified as a 62-year-old man with the surname of Fan. He had been driving a small off-road vehicle and rammed it through the gate of the sports center where people were exercising, police said. Inside his car, he tried to kill himself with a knife, inflicting wounds on his neck that left him in a coma, police said.

Police said they were unable to question the assailant, who remained in a coma and was being treated at a hospital. A preliminary investigation, based on witnesses and other evidence, found that he had been unhappy with how assets had been divided after his divorce, police said.

Authorities appeared to move swiftly to control the spread of information, reflecting a long-standing fear of drawing public criticism over how the government handles threats to public safety.

Videos of the attack and discussions on social media briefly took over the Chinese internet Monday night but were swiftly taken down by censors. Local media interviews of witnesses were also mostly removed from the internet by Tuesday evening. The incident occurred on the eve of an annual air show in the city held by the People’s Liberation Army.

Officials on Tuesday rushed to signal that the authorities were moving quickly to address broader security concerns.

Li Qiang, China’s premier, said the government must “investigate hidden risks and social conflicts.” Huang Kunming, the top Communist Party official for the southern Chinese province of Guangdong, where Zhuhai is, called for “greater efforts and more powerful measures” to protect people’s lives.