The Zetas, once the military wing of the Gulf Cartel, is now among one of the most violent groups in Mexico. The Zetas started out as an enforcer gang for the Gulf Cartel, taking their name from the radio code used for top-level officers in the Mexican army. Not only are they highly organized, but their use of brutality and shock tactics – petrol bombs, beheadings, and roadblocks – has led the United States Drug Enforcement Administration (DEA) to describe them as perhaps “the most technologically advanced, sophisticated and violent of these paramilitary enforcement groups.”