It was the summer of 2009 and my journalism lecturer told my class in Beijing that we'd be watching a documentary that day instead of receiving our usual news writing course.

Key points: There is no official ban on discussing the massacre but it can lead to repercussions

There is no official ban on discussing the massacre but it can lead to repercussions Youth find out about the massacre through pop culture, using VPNs or even from teachers

Youth find out about the massacre through pop culture, using VPNs or even from teachers Some have trouble coming to terms with the fact that their government killed its own citizens

"You guys watch it quietly by yourself, I'll be away for a while," the lecturer said, before he pressed play on the projector and walked out of the classroom.

Alone in the room, the students witnessed collections of short films and images of the Tiananmen Square massacre on June 4, 1989, a date that previously held little or no significance for us.

There was the famous moment of a lone man confronting a line of tanks, masses of soldiers on the city's streets, and dead civilians lying in pools of blood.

As is the case at all Chinese schools and universities, learning about the massacre of pro-democracy protesters in and around Tiananmen Square three decades ago is definitely not part of the curriculum.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 42 seconds 42 s Students camp out in Tiananmen Square in the spring of 1989

Discussing the massacre is not officially banned, but doing so can lead to losing your job, being arrested or mysteriously disappearing, and the lecturer was taking a huge risk doing this — so much so that revealing my identity could put people back home at risk.

As a child, we lived by Tiananmen Square in 1989, and before entering the classroom that day, the only time I had heard any mention of it was from my parents who would casually refer to it as a "student riot" or the "June 4 incident", and usually in passing responding to things like me whinging about the traffic.

"There was no bus running on Chang'an Avenue during the students' riot when you were little — public transport was cancelled," my mother told me.

"You should appreciate how much better Beijing's traffic is these days instead of complaining."

But for many of the students, it was the first time they'd ever heard of the night let alone seen footage of such a massacre in our very own backyard, and it was startling with many students even shedding tears.

I, for one, was of the view that this so-called documentary was generally a one-sided piece of Western propaganda that excluded the Chinese point of view and presented the night in a way that bent the truth.

For starters, the documentary was in English and how could Western journalists have evidence of something even we locals didn't have — additionally, journalism school in China teaches that the media in general often tries to manipulate facts in this way.

Chinese soldiers began clearing Tiananmen Square of pro-democracy protesters on June 3, 1989. ( AP: Jeff Widener )

"Why did these people from overseas think they knew better than me?" I remember thinking.

When the lecturer returned after roughly under an hour, the main feeling among the students was a mixture of shock but mostly disbelief.

He told us that it was important for us to see and know, without specifying why, calmly demanded that we don't tell anyone about what he just showed us, and proceeded to teach class from that day forward without speaking of it again.

When I got home that night, I asked my parents what exactly a student riot was and what happened during this June 4 incident, but they brushed aside and refused to answer my questions.

After a brief silence, my parents changed the subject, and I got carried away with the conversation.

This is the way the Tiananmen massacre is passed on, remembered and spoken about in China: through the memories of its witnesses, behind closed doors, in code, or in ways that shall not be repeated or named.

'It can't all be true': The pervasiveness of censorship

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 6 minutes 21 seconds 6 m Former soldier Xiaoming Li says he never fired a shot but is still wracked with guilt

It took me a long time before I started to really think about and believe the devastating images I saw on that hot summer day 10 years ago.

Back in 2009, China's Great Firewall was not as impenetrable as it is today, so not long after the class, I began curiously searching "June 4" and "how many were killed during the June 4 incident?" — the answers suggested there may have been a significant death toll, hundreds if not thousands.

It was difficult to come to terms with the fact that my own government had killed its own people and covered it up — growing up, we all knew there was censorship, but didn't fully realise how powerful and pervasive it was.

"It can't be all true," I reassured myself.

Today, even the phrase "Tiananmen massacre" remains a mind-blowing concept for my generation, who grew up consuming the heavily censored content produced in Communist China.

The student-led pro-democracy protests became China's greatest political upheaval since the end of the Cultural Revolution more than a decade earlier. ( AP: Sadayuki Mikami )

Many of us ended up discovering its existence through unexpected means, with anti-government art installations or pop culture being another important source of knowledge.

For example, recently some fans of Hong Kong singer Jacky Cheung Hok-yau discovered the significance of the date after one of his most popular songs — called The Way of Man and written after the massacre — was removed from music streaming platforms in China last year.

"How could the soil of the old world became waves in the sea of blood?" the song's lyrics say, and curious fans immediately search for why the song was censored using VPNs to break through the firewall and get on Google.

The student-led rallies were peaceful but as the army advanced some protesters attempted to counter the attack by creating makeshift barricades. ( AP: Jeff Widener )

But as China's censorship mechanisms become increasingly robust, knowledge about the Tiananmen massacre — as well as other politically sensitive issues — is more difficult for ordinary people to acquire.

Well-educated elites in big cities are more likely than people in rural areas to be equipped with the funds and technological know-how to use a VPN.

According to available data, only 4 million people out of China's 800 million internet users regularly get on Google, and at least 1.5 million of those users are based in wealthy regions like Beijing, Shanghai and Guangdong.

One of the most common ways for young Chinese people to discover the truth about that day is by travelling overseas.

A friend from Hebei province recently told me her memories of seeing practitioners of Falun Gong, a spiritual discipline banned since 1999 and labelled an "evil cult" by Beijing, holding banners displaying an image of a tank at Tiananmen Square crushing dissent.

At first, she too believed it was the work of "malicious" people trying to disgrace China with lies, and she said it was only after her mother and I confirmed it was the truth that she dropped the idea.

For me, the moment of revelation came three years after watching that documentary in 2012, when I began to work as a journalist in China.

It was only after speaking with trusted colleagues and interviewing sources who saw students killed with their own eyes, that I came to fully believe that a massacre occurred in my country's recent past.

I realised that, in China, the Tiananmen Square massacre existed in a strange void created by a mix of government censorship and people's fear of repercussions.

It was a massive wake-up call for me about the power of the state and how humans carry and pass on memories.

Estimates of the number of casualties range from hundreds to thousands of people. ( AP: Terril Jones )

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