[4][5] On 2 September 2011, Mejía González and Rafael Cárdenas Vela, two leaders of the Rojos, ordered the assassination of the drug lord Samuel Flores Borrego, who commanded the Metros, another faction within the Gulf cartel.

[1] 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.

[6] 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.

[6] The infighting between the Metros and the Rojos of the Gulf cartel began in 2010, when Juan Mejía González, nicknamed El R-1, was overlooked as the candidate of the regional boss of Reynosa and was sent to the "Frontera Chica," an area that encompasses Miguel Alemán, Camargo and Ciudad Mier – directly across the U.S.–Mexico border from Starr County, Texas.

[6] Unconfirmed information released by The Monitor indicated that two leaders of the Rojos, Mejía González and Rafael Cárdenas Vela, teamed up to kill Flores Borrego.