 Osiel Cárdenas Guillén, his brothers Antonio Cárdenas Guillén, Mario Cárdenas Guillén, and Jorge Eduardo Costilla Sánchez have all been captured and incarcerated during Felipe Calderón's administration.In 1999, Gulf Cartel's leader, Osiel Cárdenas Guillén, hired a group of 37 corrupt former elite military soldiers to work for him.These former Airmobile Special Forces Group (GAFE), and Amphibian Group of Special Forces (GANFE) soldiers became known as Los Zetas and began operating as a private army for the Gulf Cartel.