SHANGHAI: Shares in Chinese cybersecurity company 360 Security Technology (601360.SS) plunged on Thursday after the firm announced that its billionaire founder Zhou Hongyi and his wife were divorcing and that he would give her a 6.25% share.

Shares in 360 Security, China’s largest provider of cybersecurity products, fell by as much as 7.8%, its biggest one day fall since February.

The company on Tuesday issued a statement saying Zhou would give a 6.25% share to Hu Huan, which was worth about 9 billion yuan ($1.3 billion) based on 360 Security’s closing price that day.

Thursday marked the first trading after the announcement, as markets were shut on Wednesday for a public holiday.

Prior to the divorce, Hu had no shares in the company. The marriage ended on friendly terms, and their separation will not affect the company’s operations, the company said.

Zhou founded 360 Security Technology in 2005. The company was listed on the New York Stock Exchange in 2011 and returned to Chinese stock markets in 2018 through a back door listing.

He will remain as the company’s controlling shareholder after the transfer, with a 5.24% stake under his name, and a 46.14% stake through Tianjin Qixin Zhicheng Technology Co. Ltd., whose largest shareholder is Zhou.

360 Security’s share price has nearly tripled so far this year. The company has said it is working on artificial intelligence technologies, latching on to a buzz created by hit U.S. chatbot ChatGPT.