 According to some writers, like Peter Dale Scott, the Guadalajara Cartel prospered largely because it enjoyed the protection of the Mexican DFS intelligence agency, under its chief Miguel Nazar Haro.Félix Gallardo, a former federal police officer, started working for drug traffickers brokering corruption of state officials, and his partners in the Cartel, Rafael Caro Quintero and Ernesto Fonseca Carrillo, who previously worked in the Avilés criminal organization, took control of the trafficking routes after Avilés was killed in a shootout with the police.Juan Matta-Ballesteros was the Guadalajara Cartel primary connection to the Colombian cartels, he had originally introduced Felix Gallardo's predecessor, Alberto Sicilia-Falcon to Santiago Ocampo of the Cali Cartel, the head of one of the largest U.S. cocaine smuggling rings.