"Z" explanation

( Tomas Bravo, Reuters )

The letter "Z" is seen painted on a hill next to the toll booth at the freeway between Monterrey and Torreon, in the Mexican state of Coahuila March 13, 2010. The "Z" refers to the Zetas drug cartel. In just four years, Monterrey, a manufacturing city of 4 million people 140 miles (230 km) from the Texan border, has gone from being a model for developing economies to a symbol of Mexico's drug war chaos, sucked down into a dark spiral of gangland killings, violent crime and growing lawlessness.