Nevertheless, other sources also reveal that Antonio Cárdenas Guillén, brother of Osiel and one of the successors of the Gulf Cartel, was addicted to gambling, sex, and drugs, leading Los Zetas to consider his leadership as a threat to the organization. Other reports mention, however, that the rupture occurred due to a disagreement about who would take on the leadership of the cartel after the extradition of Osiel. The candidates of the Gulf Cartel were Antonio Cárdenas and Jorge Eduardo Costilla Sánchez, while Los Zetas wanted the leadership of their current head, Heriberto Lazcano Lazcano. Other sources, however, mention that the Gulf Cartel began looking to form a truce with their Sinaloa Cartel rivals, and Los Zetas did not want to recognize the treaty settlement, which led them to act independently and eventually break apart. On the other hand, other sources reveal that Los Zetas separated from the Gulf Cartel to ally with Beltrán-Leyva Cartel, which led to conflict between them. Other sources mention that what initiated the conflict between them was when Samuel Flores Borrego, alias "El Metro 3", lieutenant of the Gulf Cartel, killed Sergio Peña Mendoza, alias "El Concorde 3", lieutenant of Los Zetas, due to a disagreement for the drug corridor of Reynosa, Tamaulipas, whom both protected. Soon after his death, Los Zetas demanded the Gulf Cartel to hand over the killer, but they didn't, and observers believe that triggered the war.