Oct. 28, 2002: University of Arizona

Oct. 28, 2002: Robert Flores Jr., 41, who was flunking out of the University of Arizona nursing school, shot and killed three of his professors before killing himself. Pictured: University of Arizona nursing professor Barbara Monroe is shown in this undated photo from the University of Arizona in Tuscon, Arizona. Monroe was one of three professors shot and killed by Flores.

Credit: Photo by University of Arizona/Getty Images