May 4, 1970: Four students were killed and nine wounded by National Guard troops called in to quell anti-war protests on the campus of Kent State University in Ohio. Oct. 28, 2002: Failing University of Arizona Nursing College student and Gulf War veteran Robert Flores, 40, walks into an instructor’s office and fatally shoots her. A few minutes later, armed with five guns, he enters one of his nursing classrooms and kills two more of his instructors before fatally shooting himself. Sept. 2, 2006: Douglas W. Pennington, 49, kills himself and his two sons, ages 26 and 24, during a visit to the campus of Shepherd University in Shepherdstown, W.Va. Jan. 16, 2002: Graduate student Peter Odighizuwa, 42, recently dismissed from Virginia’s Appalachian School of Law, kills the dean, a professor and a student before being tackled by students. The attack also wounds three female students. Aug. 15, 1996: Frederick Martin Davidson, 36, a graduate engineering student at San Diego State, is defending his thesis when he pulls out a handgun and kills three professors. Fatal shootings at U.S. colleges or universities in recent years. April 16, 2007: A gunman kills 32 people in a dorm and a classroom at Virginia Tech in Blacksburg, Va. The gunman later dies. Aug. 1, 1966: Charles Whitman points a rifle from the University of Texas at Austin’s tower and begins shooting in a rampage that goes on for 96 minutes. Sixteen people are killed, 31 wounded. Nov. 1, 1991: Gang Lu, 28, a graduate student in physics from China, reportedly upset because he was passed over for an academic honor, opens fire in two buildings on the University of Iowa campus. Five university employees killed, including four members of the physics department; two other people are wounded. The student fatally shoots himself.