June 4th marks the 29 year anniversary of the Tiananmen Square (天安門) Massacre, "Chinese troops storm through Tiananmen Square in the center of Beijing, killing and arresting thousands of pro-democracy protesters. The brutal Chinese government assault on the protesters shocked the West and brought denunciations and sanctions from the United States." 
"In May 1989, nearly a million Chinese [civilians], mostly young students, crowded into central Beijing to protest for greater democracy and call for the resignations of Chinese Communist Party leaders deemed too repressive. For nearly three weeks, the protesters kept up daily vigils, and marched and chanted. Western reporters captured much of the drama for television and newspaper audiences in the United States and Europe. On June 4, 1989, however, Chinese troops and security police stormed through Tiananmen Square, firing indiscriminately into the crowds of protesters... Reporters and Western diplomats on the scene estimated that at least 300, and perhaps thousands, of the protesters had been killed and as many as 10,000 were arrested."
The savagery of the Chinese government’s attack shocked both its allies and Cold War enemies. Soviet leader Mikhail Gorbachev declared that he was saddened by the events in China. He said he hoped that the government would adopt his own domestic reform program and begin to democratize the Chinese political system." 
Nobody outside of the Chinese government knows for sure how many civilians were killed in the massacre, or had died slow death in the gulags. Many of those who were arrested are never seen by their families again. Others were executed publicly.
In China, there is complete blackout of the event, as if it never happened. It's banned from textbooks, and mention of it is suppressed by the government. I can personally testify to this: I happened to be visiting Hong Kong (a Chinese territory since 1997) during the 25th anniversary of the event. I remember seeing vigils and marches, with people flying the Republic of China flags, which is held as a symbol of revolution (originally the revolutionary flag when the last Imperial Dynasty was overthrown in 1911, and currently the national flag of Taiwan). At the time, I didn't make the connection, and don't recall seeing the local news mention an event involving tens of thousands of people throughout the territory. Only after returning to the US, did I see articles about the observance.
The Trump administration is calling the Chinese government to owe up to what they had done 29 years ago:
“We join others in the international community in urging the Chinese government to make a full public accounting of those killed, detained or missing,” Pompeo said, according to Reuters.
In response, China’s foreign spokeswoman Hua Chunying said it had lodged “stern representations” with the United States, which it accused of “gratuitous criticism.”
"The U.S. Secretary of State has absolutely no qualifications to demand the Chinese government do anything,” Hua said, according to Reuters.
Tens of thousands of people are expected to gather later in Hong Kong, the only place in China where public commemorations take place, to mark the anniversary.
China director at Human Rights Watch, Sophie Richardson, said Chinese authorities were trying to stop commemorations of the Tiananmen crackdown by arresting a number of activists.
“The only way to remove this stain on China is to own up to it,” she said. 
Through HK was how much of the eye-witness accounts had came out of China. While most of HK citizens are ethnically Chinese, at the time HK was a British territory, and therefore British subjects.
And Hong Kong remembers. "More than 100,000 people gathered in Victoria Park in Hong Kong to mark the 29th anniversary of the Tiananmen Square crackdown in Beijing, according to the organisers of the annual candlelight vigil. The vigil has been held annually since 1990 and is organised by the Hong Kong Alliance in Support of Patriotic Democratic Movements of China."
What is the lesson to take from this? 29 years ago, students in China died protesting against their government restricting their freedom. Now, students in America are protesting for the government to take away others' freedom. Appreciate the individual rights we have as Americans. Appreciate our right to free speech. Hold it dearly, defend it with every breath we have. Look at Venezuela, China, Cuba, North Korea, and other Communist and Fascist nations. Look at what happens when the people give the government ultimate power in the "name of the people."