Reputed leader of Los Zetas cartel in Mexico 's Gulf state reportedly in gunbattle . Arellano Dominguez dies in firefight with authorities , attorney general says . Mexico considered thousands of Los Zetas 's most advanced and violent drug cartels .
Reputed leader of Los Zetas cartel in Mexico 's Veracruz state reportedly in gunbattle . Braulio Arellano Dominguez dies in firefight with authorities , attorney general says . Los Zetas considered one of Mexico 's most advanced and violent drug cartels .