Even 20 years later, the shooting, chaos and death of the final assault on Tiananmen Square remain vivid in the mind of former soldier Zhang Shijun. Today, he has become one of the few to publicly voice regret.

In bearing witness about his role in the military crackdown on the 1989 student demonstrations in Beijing, Zhang says he hopes to add momentum to calls for an investigation and reassessment of the protest movement — and to further its ultimate goal of a democratic China.

"I feel like my spirit is stuck there on the night of June 3," Zhang, 40, said in an interview at his home in the dusty northern city of Tengzhou, referring to the date in 1989 on which the final assault began.