Please answer the following question: What is the last name of the person that the CIA agent assigns the AFN operative to follow?  Answer the above question based on the context below:  El Mariachi is recruited by CIA agent Sheldon Jeffrey Sands to kill General Emiliano Marquez, a corrupt Mexican Army officer who has been hired by Mexican drug lord Armando Barillo to assassinate the President of Mexico and overthrow the government. Many years before, El Mariachi and his wife Carolina confronted Marquez in a shootout and wounded the general; in retaliation, Marquez took the lives of Carolina and their daughter in an ambush. In addition to El Mariachi, Sands persuades former FBI agent Jorge Ramírez to come out of retirement and kill Barillo, who had murdered his partner Archuleta in the past. Furthermore, AFN operative Ajedrez is assigned by Sands to tail Barillo. While monitoring Barillo's activities, Ramírez meets Billy Chambers, an American fugitive who has been living under the protection of Barillo, but can no longer stomach the horrible tasks he's been forced to carry out for him. Ramírez convinces Chambers he will provide him protection in exchange for getting closer to Barillo by tagging Chambers' pet chihuahua with a hidden microphone, and Chambers agrees to complete the deal by surrendering to U.S. authorities once Barillo has been taken down. Sands' assistant, Cucuy, originally hired to keep an eye on El Mariachi, instead tranquilizes El Mariachi and turns him over to Barillo, also offering to reveal the details of Sands's plan. Cucuy, however, is promptly killed by Chambers while El Mariachi escapes from captivity and calls his friends Lorenzo and Fideo to assist him in his mission.
Answer:
Barillo