In March 1994, an event shocked all Mexicans: the assassination of Luis Donaldo Colosio, the presidential candidate most likely to become the next President of Mexico. The presumed assassin, Mario Aburto, was captured and is currently in prison. Who killed Colosio? Was Aburto a lone assassin or was he part of a grand conspiracy to eliminate Luis Donaldo Colosio? For the first time ever, this book describes in detail the investigation to answer these questions. Citizen Zero analyzes the facts, clues, testimony of hundreds of witnesses and more than 60,000 pages of criminal investigation to determine who killed Colosio. Citizen Zero is written by Dr. Jesús Zamora Pierce, who was advisor to the prosecutors that investigated the crime: Miguel Montes and Olga Islas.