On the afternoon of 25 August 2011 , eight members of Los Zetas entered a casino in Monterrey , Nuevo León and poured gasoline on the entrance , carpets and slot machines . In less than two minutes , the assailants fled the scene and the casino was consumed . 52 were killed ; the victims , mostly women , were well-to-do civilians caught by the casino owner 's refusal to pay for protection . The alleged mastermind was a low-level member who was seeking refuge far from Monterrey , suggesting that the chain of command in Los Zetas was fragmenting . It is still unclear to what degree Lazcano and Treviño Morales were involved in the " deadliest single attack of the Calderón presidency , " but the attention the attack brought to Los Zetas was clearly unwelcome
52 were killed
2011 Monterrey casino attack
Infighting in Los Zetas