Why did the librarians of Wuhan University of Science and Technology chop and kill the self-taught students?

The general story is as follows: At 9: 00 am on October 20th, 65438/KLOC-0, a 38-year-old male librarian began to sing the same song repeatedly in a study room on the fifth floor of the library of Wuhan University of Science and Technology, which broke the quiet atmosphere. Some students asked him not to sing, so as not to affect everyone's study. Who knows that the administrator suddenly flew into a rage, took out a fruit knife and stabbed a boy and a girl. Cut more than 20 knives for girls, resulting in the death of girls and the injury of boys. After two students fell in a pool of blood, the administrator stabbed himself in the abdomen with a knife and shouted, "I don't think you can get out." It is said that the suspect suffers from mental illness.