NEW : The Tamaulipas state governor appoints a new head of public security . MEXICO CITY -- Mexico 's attorney general had previously identified Estrada Luna as one of three prime suspects behind the mass graves . He is a presumed leader of the Zetas drug cartel in northeastern Mexico . Tamaulipas is one of Mexico 's most active states when it comes to drug trafficking .
NEW : The Tamaulipas state governor appoints a new head of public security . MEXICO CITY -- He is a presumed leader of the Zetas drug cartel in northeastern Mexico . Tamaulipas is one of Mexico 's most active states when it comes to drug trafficking .