In the late 1990s,
Osiel Cárdenas Guillén, the former leader of the Gulf cartel, had other similar groups besides
Los Zetas established in several cities in Tamaulipas. Each of these groups were identified by their radio codes:
the Rojos were based in
Reynosa; the Metros were headquartered in
Matamoros; and the Lobos were established in
Laredo.
InSight Crime explains that the fundamental disagreement between the Rojos and the Metros was over leadership. Those who were more loyal to the Cárdenas family stayed with the Rojos, while those loyal to
Jorge Eduardo Costilla Sánchez, like Flores Borrego, defended the Metros. Originally, the Gulf cartel was running smoothly, but the infighting between the two factions in the Gulf cartel triggered when Flores Borrego was killed on 2 September 2011. ==References==