June 4th marks the the 20th anniversary of the Tiananmen Square incident which was one of the darkest events in modern Chinese history. In 1989, hundreds of thousands of Chinese university students peacefully gathered in Tiananmen Square to protest about government corruption and demanded political reform. After six weeks of continued protests, on June 4th, 1989 the Chinese government rolled out military tanks and troops to crackdown on the student protesters. The exact number of deaths resulting from the incident are unknown. Some sources say its in the hundreds, others say its in the thousands.
By all means, watch this 2 part documentary by AlJazeera called It happened in Tiananmen Square. This documentary explains how the Tianamen Square incident unfolded and features some of the surviving protesters speaking out about their experience in Tiananmen Square.