A massive candlelight vigil is taking place on Tuesday in the only part of China that allows dissent, Hong Kong, to commemorate the 30th anniversary of the Tiananmen Square massacre — but it may be one of the last times the moving protest ever takes place.

In April 1989, roughly 1 million pro-democracy advocates gathered in Beijing’s Tiananmen Square in the heart of the sprawling capital city. For six weeks, they pushed the communist regime to open the nation’s political system in hopes that it would move away from decades of authoritarian leadership.

That didn’t happen. Instead, Chinese troops entered the square in the early morning of June 4 and throughout the day opened fire on the protesters. Beijing has never released an official death toll, though estimates from human rights groups and foreign organizations put it anywhere from a few hundred to about 10,000.

That slaughter remains a sensitive subject for millions of Chinese people and for the government itself, which has spent the years since mostly denying that the events at Tiananmen ever took place.

Which makes the vigil in Hong Kong, a semi-autonomous city in China, such a unique and defiant event.

Every year since the massacre, pro-democracy organizers have brought thousands of people into a main square of Hong Kong on the anniversary of the event to remember those lost and to continue the fight for democracy in China. This year, around 180,000 people, one of the highest-ever totals for the protest, joined the gathering — the only place in China that those who want to memorialize the tragedy and push for change could do so.

The problem is that 2019 may be one of the vigil’s last years. That’s because Beijing — which is supposed to leave the city mostly alone — wants to exert more control over it. Which means the freedom of expression enjoyed in Hong Kong, the very thing that makes the ceremony possible at all, may soon become a thing of the past.

“This may be the last time we get to express our dissent freely,” 19-year-old college student David Chung told the South China Morning Post on Tuesday.

“The death of Hong Kong”

After taking over Hong Kong in a war in the 1800s, Britain returned it to China in 1997 with an important stipulation: The city would govern itself for 50 years before officially folding back into the mainland. So until 2047, the expectation was that the area would function under the principle known as “one country, two systems.”

But Beijing clearly isn’t waiting that long.

At China’s direction, the Hong Kong government in recent years has quashed the city’s democratic movement, blocked opposition candidates from running for elected office, and put down nearly all protest movements. And it may soon get worse: There’s a proposal to amend a Hong Kong extradition law that would allow someone arrested in the city to face trial in another part of China.

That would all but cement Beijing’s authority in the supposedly semi-autonomous city.

“When the legislation passes — which now seems near certain, and imminent — it will spell the death of Hong Kong as the world has known it,” Ray Wong Toi-yeung, a political activist from the city, wrote for the New York Times on Tuesday.

That means the candlelight vigil that has allowed thousands to keep the memory of those killed in Tiananmen Square alive may soon fall victim to China’s crackdown on freedom of expression.

Of course, that hasn’t stopped the nearly 200,000 protesters from attending Tuesday’s ceremony, and it certainly won’t stop activists from pushing back against China’s growing influence in the years to come.

“For the future of Hong Kong, we must fight to the end,” Ho Chun-yan, the head of a pro-democracy group in the city, said at the vigil.