In a statement on the Chinese social media platform Weibo on Saturday, Vitasoy said a staff member had circulated a memo that it described as “extremely inappropriate” without authorisation, and the company reserved the right to take legal action.

Shares of Vitasoy were down 14.6% at HK$25.1, levels not seen since April 2020.

It was the biggest single-day drop since its listing in 1994.

The broader Hong Kong market was flat.

The staffer’s memo offered condolences to the family of a 50-year-old Vitasoy worker who had stabbed a police officer, 28, and then killed himself on Thursday, the anniversary of the former British colony’s return to Chinese rule.

Police and security officials have described the stabbing as a terrorist attack by a lone wolf, saying a computer they seized from his home showed he had been “radicalised”.

Police did not provide further details about his alleged radicalisation.

The officer’s condition has improved to serious from critical.

The Vitasoy worker’s memo triggered a flood of online calls for a boycott of the company, which gets two-thirds of its revenue from mainland China.

Mainland actor Gong Jun, who previously endorsed a Vitasoy lemon-flavoured drink, announced late on Friday he was ending commercial cooperation with the company, said Global Times, a tabloid published by the ruling Chinese Communist Party’s official People’s Daily newspaper.

His announcement followed that of another mainland Chinese actor, Ren Jialun, who said he was also ceasing cooperation with Vitasoy, the newspaper added.

Hong Kong authorities warned yesterday that advocating for people to mourn for the attacker was no different from “supporting terrorism” and criticised parents who took children to mourn him.