Who are Los Zetas?
Former leader of drugs Mexican cartel "Los Zetas", Miguel Angel Trevino Morales, aka "El Z-40" escorted by marines after his arrest
Mexico's largest criminal gang - began in 1990s as enforcement arm of drugs gang Gulf Cartel
Broke away to form own group in 2010
Originally comprised of ex-army men who deserted their positions
Named after Mexican word for letter "Z"
Ex-leader Miguel Angel Trevino Morales (pictured), known as "Z-40", captured in July 2013
Drug trafficking makes up 50% of revenue - also engaged in debt collecting, kidnapping, extortion
Renowned for brutality, in particular beheadings