An act of infamy that echoes down the ages

Eighty years ago, Japanese troops began a killing spree in East China that cost an estimated 300,000 lives, as Zhao Xu reports.

Wu Xianbing was 21 when he was asked to play a video cassette whose contents scar him to this day.

"I was a technician at Nanjing University and Gao Xingzu, the professor I was assisting, was a member of the history department," the 53-year-old recalled.