Mullen joined the
Chicago Tribune after graduating in 1967. His early years were largely spent as a nightside police reporter and as a rewriteman. When the
Tribune had the opportunity to place a reporter undercover in the Board of Election Commissioners, Mullen was selected because his face was not a familiar one in
Chicago City Hall. During the summer and fall of 1974, Mullen and Ovie Carter were travelled across Africa and India. Their journey resulted in the series of illustrated articles "The Faces of Hunger", which brought Mullen a second
Pulitzer Prize in 1975. Over the years, the journalist was awarded the
Jacob Scher Award for Investigative Reporting; a three-time Edward Scott Beck Award winner;
School of Journalism and Mass Communication University of Wisconsin Award. From 1978 to 1981, Mullen served as the chief correspondent of the
Chicago Tribune London Bureau, traveling extensively in Europe, the Middle East and Asia. In 1987 and 1988, Mullen compiled an award-winning series on refugees after spending a year traveling to refugee camps in Africa, the Middle East, Asia and Central America as a staff writer for the
Chicago Tribunes Sunday Magazine. In the 1990s, he turned to writing on and reporting on cultural affairs and the natural sciences, an assignment that twice took him to Antarctica and the South Pole and on extended trips to the Peruvian Amazon to save a pristine forest from oil drilling. ==Personal life==