Just 22-years old at the time, Li was a student in Beijing. His college was a few kilometres from Tiananmen Square, and he, along with fellow students, went to join in the protests.
"Before I got there, I heard the bullets. I heard the gunfire," he says. "I said, 'That couldn't be real bullets. It must be some kind of rubber bullets, otherwise, how many people are going to die?'"
The Chinese military had opened fire at thousands of student protesters at the pro-democracy camps that had occupied the square.
Once inside the square, Li says the noise from the tanks and machine guns was overwhelming.
Li watched as people fell to the ground on both sides of the street. His clothes were covered in blood, from carrying injured people, trying to get them to hospital.
Officially, the Chinese government claims 246 people died, but the real number could be as high as 2000, he estimates.
"Before that day, the majority of the Chinese people, probably the people around the world, didn't realize a bunch of people are ruining [China]," says Li.
Li says witnessing the Tiananmen Square massacre mobilized him into action.
"That day, that night, it changed many peoples lives," he says.
"Before that, I was not very involved in political issues in China. I tried to be a scholar. After that night, I become more devoted in the Chinese democratic movement, and became a full-time activist."
Li says being a pro-democracy activist in communist China was nearly impossible.
By the mid-90s, many of his peers were either in jail, or had left the country. He moved to Hong Kong in 1995, and then in 1997, when control of Hong Kong was handed over to the Chinese, he immigrated to Vancouver.
Crackdown on memorials in Beijing
The 25th anniversary of the massacre in Tiananmen Square is being remembered worldwide, but the Chinese government is attempting to crack down on public memorials within its own borders.
Dozens of government critics have been detained, and in Beijing, police and paramilitary troops are patrolling pedestrian overpasses and streets surrounding the square.
But while the events of June 3 and 4 are barred from public discussion in China, Li says it has become more difficult for the Chinese government to erase the days events.
"They try to block the news of that day, try to prevent people to know the truth of that day, and they try to make the nation forget that day," he says. "But, with the internet, they couldn't succeed. They couldn't prevent people from knowing the truth."
Li says 25 years later, he has renewed hope for the next generation of pro-democracy activists in China.
"We're using the internet tools to build a new network of activists," he says. "This time, it's very promising. We're connecting people, and accumulating our strength."
In Vancouver, a candlelight vigil will take place near the Chinese Consulate on the night of Wednesday, June 4, to commemorate the events that took place in Tiananmen Square.