A cartel in Mexico has issued a death threat to U.S. law enforcement via a banner attached to an overpass in Mexico, across the border from El Paso, Texas. The banner, written in Spanish, translates to: “Warning: This is for the local, state, ministries, and national guard and for the American [expletive] from immigration. “Stop [expletive] with the smugglers or we will kill you. The bullets cross the river and the wall, so stop [expletive] around.” The banner is signed: “Yours, the very best of all Juarez.” Juarez is the Mexican city located across the border from El Paso. A photo of the banner was sent to former Immigration and Customs Enforcement (ICE) special agent Victor Avila on July 15 by a source in Mexico, who posted it to Twitter (warning, expletive language). Avila worked in ICE Homeland Security Investigations, the agency’s investigative arm. In 2011, he survived a violent …