Arturo Guzmán Decena, founder of Los Zetas and high-member of the Gulf Cartel, is killed in a shoot-out with the Mexican Army and the police.

Arturo Guzmán Decena, also known by his code name Z-1, was a Mexican Army Special Forces officer and high-ranking member of Los Zetas, a criminal group based in Tamaulipas. He defected from the military in 1997 and formed Los Zetas, the Gulf Cartel's former paramilitary wing, under the leadership of the kingpin Osiel Cárdenas Guillén.

Los Zetas is a Mexican criminal syndicate and designated terrorist organization, known as one of the most dangerous of Mexico's drug cartels. They are known for engaging in brutally violent "shock and awe" tactics such as beheadings, torture, and indiscriminate murder. While primarily concerned with drug trafficking, the organization also ran profitable sex and gun rackets. Los Zetas also operated through protection rackets, assassinations, extortion, kidnappings and other illegal activities. The organization was based in Nuevo Laredo, Tamaulipas, directly across the border from Laredo, Texas. The origins of Los Zetas date back to the late 1990s, when commandos of the Mexican Army deserted their ranks and began working as the enforcement arm of the Gulf Cartel. In February 2010, Los Zetas broke away and formed their own criminal organization, rivalling the Gulf Cartel.

The Gulf Cartel is a criminal syndicate, drug trafficking organization, and U.S.-designated Foreign Terrorist Organization, which is perhaps one of the oldest organized crime groups in Mexico. It is currently based in Matamoros, Tamaulipas, directly across the U.S. border from Brownsville, Texas.

The Mexican Army is the combined land and air branch and is the largest part of the Mexican Armed Forces; it is also known as the National Defense Army.