article_snippet: The US Drug Enforcement Administration, which had the notorious Zetas drug cartel leader Omar Trevino Morales on The US Drug Enforcement Administration '
article_snippet: the Zetas' carved a path of brutality, bloodshed and mutilated bodies across northern Mexico during the Zetas' turf battles with the rival Gulf cartel, claiming upwards of 100,000 lives since 2007.
article_snippet: Among the most notorious incidents attributed to the Zetas' are the massacres of dozens of migrant workers, an arson attack on a Monterrey casino in 2011 that killed 52 and the dumping of 49 decapitated bodies near the same city in 2012.
article_snippet: Once the flashpoint for the worst of the violence, security in northern Mexico has improved considerably, except for the lawless northeastern border state of Tamaulipas, said Raul Benitez.
article_snippet: Founded in the late 1990s by deserters from an elite Mexican army unit, the Zetas' initially acted as enforcers for the powerful Gulf cartel, based along the border with Texas and one of the oldest criminal syndicates in Mexico.
article_snippet: But the group struck out on the group own in early 2010, setting off the most violent phase in Mexico's drug war.
article_snippet: Murder epidemic: Soldiers arrive to reinforce an operation in the suburb of Guadalupe in Monterrey October 26, 2009. 
article_snippet: the Zetas' carved a path of brutality, bloodshed and mutilated bodies across northern Mexico during the Zetas' turf battles with the rival Gulf cartel .
article_snippet: Massacre: Gunmen of the rival Gulf cartel attacked the Casino Royale in August 25, 2011 where 54 people were killed in Nuevo Leon's capital Monterrey .