Thousands of protesters swarmed Hong Kong’s Victoria Park on June 4 despite police refusing permission for the annual gathering, citing concerns about the spread of COVID-19 coronavirus.

Three organizers of the vigil—Lee Cheuk-yan, Albert Ho, and Richard Tsoi—plus media entrepreneur Jimmy Lai have been informed by police that they will face charges over the gathering, The South China Morning Post reported.

Lee—the chairman of the Alliance in Support of Patriotic Democratic Movements of China—wrote on Facebook that officers told him he would soon be summoned to court for inciting others to take part in the June 4 event. Ho said he had received a similar notification.

Lee said the charges were expected as direct “retaliation” for the event, which police tried to block this year for the first time. Protesters vowed to hold a series of smaller events regardless.

“When you look at the overall Hong Kong situation, police are abusing their power to arrest, the Department of Justice is abusing its power to prosecute and trying to [intimidate] the people of Hong Kong when they exercise our right to assembly,” Lee said, according to the Post.

Ho denied encouraging an official assembly. “We were only asking people to go to the park to commemorate the Tiananmen crackdown by themselves,” he said.

The event was held as Chinese officials pushed for a new national security law that would effectively criminalize anti-government dissent in the semi-autonomous territory following a year of pro-democracy and anti-Beijing unrest.

Hong Kong and Macau are the only places in China where the Tiananmen massacre—in which soldiers killed hundreds, perhaps thousands, of pro-reform and pro-democracy protesters in Beijing in 1989—can be commemorated. Beijing has tried to scrub the atrocity from the national memory and criminalize its mention.

Pro-democracy activists warned that refusing permission for the commemoration was a sign of things to come for anti-China protesters in Hong Kong. Last month, Chinese legislators approved the national security bill that will ban treason, secession, sedition and subversion against the Chinese Communist Party regime.

Chinese officials circumvented local representatives in Hong Kong’s Legislative Council, keen to avoid a repeat of 2003 when a proposed national security bill failed in the face of mass public protests. The legislation is expected to be put in place by September at the latest.