El Karis's death marked one of the earliest conflicts that would eventually result in the separation of the Gulf Cartel and their armed wing, Los Zetas, in 2010.

After the Gulf Cartel's supreme leader Osiel Cárdenas Guillén was arrested in 2003 and extradited to the United States in 2007,[1][2] the control of the criminal organization was handed over to Jorge Eduardo Costilla Sánchez (alias El Coss), an ex-policeman from Tamaulipas; to Antonio Cárdenas Guillén (alias Tony Tormenta), his brother; and to Heriberto Lazcano Lazcano, who left the Mexican Army special forces in 1998.

[7] Until 2006, El Karis's brother was considered among the Gulf Cartel's most influential drug traffickers, but he was forced to retire after several leaders from the organization ousted him because of cocaine addiction and illness.

[8] During his reign as the crime boss of Reynosa, El Karis reportedly forced businesses in the city to pay protection rackets and intimidated journalists who dared to write about his criminal organization.

[9] El Karis was a regional boss of the Gulf Cartel in Matamoros, Reynosa, and Nuevo Laredo, and had some influence in the city of Monterrey.

[10] Violence started at around 11:00 a.m. when law enforcement officers intercepted a convoy of vehicles filled with gunmen that travelled through a residential neighborhood in Reynosa.

[15] To keep his organization afloat and protect himself from any attacks, Cárdenas Guillén sought for recruits in the Mexican military to create his private unit of bodyguards.

[15][16] But when Cárdenas Guillén was arrested in 2003 and extradited to the United States in 2007, Los Zetas and the Gulf Cartel tried to fill the leadership vacuum with their respective commanders.

After several conflicts and disagreements, Gulf Cartel and Los Zetas ended their alliance in early 2010, prompting an all-out war between both groups in Tamaulipas and its neighboring states.