Timeline of tragedy

1. Oct 28, 2008: A senior student, Fu Chengli, from Beijing's University of Political Science and Law, stabs Professor Cheng Chunming with a kitchen knife in a classroom while he is giving a lecture. Cheng dies despite prolonged resuscitation attempts.

2. Oct 21, 2008: Pan Weixian, a teacher from Panxi Middle School in Zhejiang province, is pushed off a cliff by her student Ding Yuzhen on their way to a home visit with his parents. When he goes down and finds Pan is still alive, he strangles her to death with a rope.

3. Oct 4, 2008: 17-year-old student Li Ming stabs head teacher Hao Xudong to death in his classroom at Shuozhou Middle School, Shanxi province.