Among a crowded field of brutal drug cartels that dominate Mexico's lucrative drug trade, there are few that are more fearsome than Los Zetas.
This notorious gang comes from the same region where four American tourists were kidnapped in the past few weeks with two killed.
Some of the worst atrocities can be traced back to this gang of cut throats, such as the 2011 San Fernando massacre, where 193 bus passengers were kidnapped and killed.
