Editor 's note : Journalist Karl Penhaul spent several weeks tracking the gangs of the Mexican underworld , the corrupt officials who support them and the cops trying to halt the violence . Mexico police round up gang suspects in Juarez , across the border from El Paso , Texas . CAMARGO , Mexico ( CNN ) -- There are no welcome signs on the approach to Camargo . It 's a hardscrabble Mexican border town and home turf for `` Los Zetas , '' a gang of hitmen and corrupt former special forces cops on the bankroll of the Gulf Cartel . Local journalists explained if we went there we 'd be getting `` tangled up in the hooves of the horse . '' They said Zeta gunmen recently smashed one reporter 's fingers with a hammer as a warning to the media to stay away . The plaza was deserted -- for a few minutes at least . Then the throb of engines broke the Sunday morning peace . Scores of pickup trucks with heavily tinted windows began circling . Occasionally a window would crack open . We were clearly being watched . A black SUV pulled up alongside the soda stand . One of the occupants stepped out . First I saw the ostrich skin cowboy boots , then the highly polished 9 mm pistol strapped to his side . It was loaded with a longer-than-usual ammunition clip , custom-made to pack extra bullets . It was a brazen flouting of Mexican law to carry a gun that way . No words . Not even a stare . But his message seemed unequivocal . Our visit to Camargo lasted just 20 minutes . Taking the strong hint , we immediately left town . Much as we wanted to explore the underbelly of the drug war raging in Mexico , it was clear the capos , or bosses , and their hired guns were in no mood to talk . Their business thrives best in the shadows . Our best chance of getting some insight was to track down a cast of peripheral characters who live in the gray areas , somewhere between the extremes of right and wrong . The hospitality was little better in nearby Miguel Aleman . Customers , even an argumentative drunk , fell silent as we ordered a beer in a dingy cantina . A couple of tired-looking prostitutes retreated to a far corner . They may have been down on their luck but they knew talking to outsiders was n't worth the cost . Here the Zetas are well-known for enforcing their law of silence at gunpoint . Watch Mexican cops on the hunt for gang members » . Along this stretch of the border Los Zetas are kings . From here their bloody reach stretches far across Mexico and deep into Central America . They run immigrant smuggling , drug trafficking , prostitution rackets , video piracy and local politics . In the glitzy industrial city of Monterrey , we met a marijuana dealer smoking his own merchandise in the bathroom of a dance club . The man , whom we ca n't name for his safety , explained how he had been recruited at gunpoint two years earlier by the Zetas to be what they call a `` landowner '' ( terrateniente in Spanish ) -- in charge of cocaine distribution in a handful of neighborhoods . He said Zeta gunmen bundled him into a truck and with assault rifles aimed at his head they gave him three options -- pay them $ 100,000 , begin working for them or die . Over the next few days , he said , the same gunmen scared off or killed rival drug dealers , leaving him in charge of what he said was a $ 4,000-a-day business . It all ended , he said , when Mexican soldiers kicked down his door . He was never detained but his cover was blown . Local Zeta commanders thanked him for not ratting on them by giving him permission to retire from the business . But recently he 's gone into business for himself selling $ 2 bags of pot . He realizes working independently of the Zetas may be fatal . `` Maybe I 'm stupid or something , but I do n't know how to do anything else . If they catch me it 's simple , they 'll kill me . It 's just not allowed to work freelance , '' he said . An old friend of mine in Monterrey knew the marijuana peddler well and vouched for his story . He never made good on his promise to give us a recorded account . He went on a 24-hour drug binge . When we caught up with him again he was smoking crack , sweating profusely and paranoid his former paymasters would exact revenge . Mexico 's tit-for-tat vendettas look like uncontrolled chaos . Mob assassins are no longer content with efficient execution-style killings . Sinaloa cartel hitmen regularly place pig masks on the faces of their Juarez cartel victims . And in a grim seasonal touch , killers in Juarez decapitated a cop and placed a Father Christmas hat on his severed head . But in a sidewalk cafe in Guadalajara , `` Jose '' explains there is a clearly defined set of narco-rules that must be followed . A small-time Latin American cocaine trafficker I 've known for years introduced me to Jose . Jose is old school . He tells me he 's been in the cocaine trade since the early 1980s almost since it began , has worked internationally and done a stretch in prison . `` From the outside it might look like the cartels are just going around killing people . But on the inside there 's a code of conduct , rules . You might not want to kill somebody but you have to because it 's all about respect , '' he said . `` This can not work if there 's no respect . Above all , the capos use logic to solve the problems . '' Jose added that he believed groups of corrupt officials and law enforcement officers were using the militarization of the border region not as a means to crush the drug cartels but as a way of forcing them to pay a bigger slice of the drug profits as bribes . `` The authorities and the cartels use the rule of 10 . By that I mean for every 10 kilos of cocaine we move , we have to give three to the authorities and keep seven for ourselves , '' he explained . `` When times are bad the authorities may arrest somebody or grab an entire consignment and that 's a way for forcing up their percentage take . '' Jose 's assertion might seem like feverish conspiracy theory if it were n't for the growing list of Mexican officials , ranging from local cops and foot soldiers to generals and men at the highest levels of law enforcement , who 've been busted for allegedly profiting from the drug trade . In November , Mexico 's former drug czar was detained on suspicion that he may have accepted $ 450,000 a month in bribes from drug traffickers . He had been in charge of the attorney general 's office that specializes in combating organized crime .
`` Los Zetas '' gang of hitmen and ex-cops run rackets from U.S. border across Mexico . Reporter lasts just 20 minutes in town before message became clear : Leave now . Drug dealers reveal the rules of the cartel killers and how officials are also profiting .