 Having formed the Guadalajara Cartel in the 1970s, Caro Quintero worked with Gallardo, Ernesto Fonseca Carrillo, and Pedro Avilés Pérez by shipping large quantities of marijuana to the United States from Mexico.He was responsible for the kidnapping and murder of the U.S. Drug Enforcement Administration (DEA) agent Enrique "Kiki" Camarena, Camarena's pilot Alfredo Zavala Avelar, the American writer John Clay Walker, and dentistry student Alberto Radelat in 1985.After the murders, Caro Quintero fled to Costa Rica but was later arrested and extradited back to Mexico, where he was sentenced to 40-years in prison for murder.