Born in 1963 in Shandong province on China's northeast coast, Yang was studying in the United States when events in Beijing began to unfold. He watched the coverage of the demonstrations at Tiananmen Square on television, and at one point saw footage of police beating up students.
"I just got so emotional. I couldn't stay in the United States any longer, so I decided at that moment to go back," he said.
Yang arrived in Beijing in late May and began participating in the protests to show his support. About midnight on June 3, he heard the first gunshot and returned to the square in time to see the troops moving in. "They opened fire on either side," he recalled. "I saw about 30 people killed, the nearest one just a few yards away."
He later testified before the U.S. Congress on the Chinese military's use of force against the Tiananmen demonstrators. As a result, he was barred re-entry into the country by the Chinese government.
Unable to renew his own passport, Yang borrowed a friend's and returned to China in 2002 to observe labor unrest in the Northeast. He was arrested two weeks later at Kunming Airport in southern China while trying to leave the country, charged with illegal entry and espionage, and sentenced to five years in prison.
For the first 14 months of Yang's detention, he was put in solitary confinement and endured physical and psychological torture, he said.
In failing health, Yang was eventually transferred to another prison, where his ordeal became only slightly easier.
"I voluntarily taught my inmates English, economics, mathematics, logic," he said in a 2008 interview. "I actually wrote a textbook for logic in Chinese calligraphy and coached the basketball team for more than two years. Almost all the inmates called me 'teacher,' and many guards became my friends. Thanks to their sympathy and protection, I was able to organize a Bible study group and helped baptize three inmates."
After his release in 2007, Yang returned to the United States, where he earned Ph.D.s in mathematics from the University of California, Berkeley, and in political economy from Harvard's Kennedy School of Government. He also founded the U.S.-based Foundation for China in the 21st Century, an organization geared toward promoting greater human rights and political freedoms inside China.
In March 2008, Yang founded another U.S.-based organization, Initiatives for China, to serve as a bridge between pro-democracy groups inside China and human rights activists around the world. To protest the 2008 Summer Olympics in Beijing, Yang walked more than 500 miles between his home in Boston and Washington D.C., to draw attention political prisoners in China. Similar "citizen walks" are taking place in China to commemorate the 20th anniversary of the Tiananmen crackdown, he said.