Lu was a 28-year-old Chinese graduate student at the University of Iowa who had received his doctoral degree in physics and astronomy from the university in May 1991. In 1984, 18-year-old Lu began studying physics at Peking University in Beijing, where he passed the CUSPEA exam and was admitted to study in the United States, becoming a graduate student at the University of Iowa. As a graduate student, Lu was primarily a loner who was perceived by at least one other graduate student to have a psychological problem if challenged and was reported to have had abusive tantrums. Lu was infuriated because his dissertation, titled Study of the "Critical Ionization Velocity" Effect by Particle-in-Cell Simulation, did not receive the prestigious D.C. Spriestersbach Dissertation Prize, which included a monetary award of $2,500. The Tiananmen Square protests of 1989 led many Chinese students to become eager to stay in the United States, and Lu believed that winning the prize would have made it easier for him to get a job and not have to return to China. Normally, Lu would have gotten a postdoctoral researcher position, but there was not enough money to support him.
In the months prior to the shooting, Lu was still living in Iowa City and wrote five letters explaining the reasons for his planned actions. According to university officials, four of the letters were in English and one written in Chinese, intended to be mailed to news organizations. The letters have never been released to the public.
On Friday, November 1, 1991, Lu attended a meeting for the theoretical space plasma physics research group in a conference room on the third floor of Van Allen Hall at the university's campus. A few minutes after the meeting began, Lu shot three attendees of the meeting with a .38-caliber revolver, then proceeded to the second floor to shoot the chairman of the department in his office. Those who were shot in Van Allen Hall were:
- Christoph K. Goertz, professor of physics and astronomy,Lu's dissertation chairperson and one of America's leading theoretical space plasma physicists
- Robert A. Smith, associate professor of physics and astronomy, also on Lu's dissertation committee
- Linhua Shan, a post-doctoral research investigator and the winner of the Spriestersbach prize; Shan had once been Lu's roommate
- Dwight R. Nicholson, chairman of the physics and astronomy department, and one of Lu's dissertation committee members
After the shootings at Van Allen Hall, Lu walked three blocks to Jessup Hall to the office of T. Anne Cleary, an associate vice president for Academic Affairs and grievance officer at the university, and shot her in the head. Lu had filed several grievances about not being nominated for the Spriestersbach prize. Cleary died the following day at the University of Iowa Hospital. Lu then shot Miya Rodolfo-Sioson, a 23-year-old student temporary employee in the Office of Academic Affairs, for unknown reasons. Rodolfo-Sioson survived but was left paralyzed from the neck down, and died from inflammatory breast cancer in 2008. Lu had intended to kill university president Hunter Rawlings III, but he was attending the Iowa/Ohio State football game in Columbus, Ohio at the time. Gang Lu was found in room 203 of Jessup Hall with a self-inflicted gunshot wound to the head, and he died shortly after police arrived.