Gulf Cartel
Both of the Gulf Cartel leaders ignored the command, and Treviño Morales moved swiftly to avenge the death of his former comrade. On 30 January 2010, Treviño Morales kidnapped and slaughtered 16 Gulf Cartel members in Reynosa, Tamaulipas, marking the start of the cartel war between the Gulf Cartel and Los Zetas in the Mexican states of Tamaulipas, Nuevo León, and Veracruz that has led to thousands of deaths. Los Zetas used violent and intimidatory tactics to expand, forging a reputation as Mexico's most violent drug trafficking organization. It managed to take control of most of the territories owned by the Gulf Cartel when they had essentially served as a single organization. With Treviño Morales as the second-in-command of the criminal organization, Los Zetas began killing Gulf Cartel members and other rival drug traffickers "en masse" and winning their territories.