WESLACO – A drug lord, whose drug trafficking ring is considered the largest in the world by the U.S. government, is on trial.

The empire of Joaquin 'El Chapo' Guzman stretched way beyond his home base in Sinaloa, Mexico impacting the southern US-Mexico border.

A trail of blood and mass graves led largely back to one man and one organization, the Sinaloa Cartel.

Art Fontes was working as an FBI agent in South Texas during the time El Chapo's organization was active in Tamaulipas.

"From 2004 to 2013, you have several thousands of people, during the Calderon administration you had approximately 50,000 victims or people that were killed due to the violence, and part of the common denominator was Chapo Guzman," he said.

He says in the 1980s, Guzman was part of the Mexican Federation. He worked his way up, "from alien smuggling, to drug trafficking, and then he became leader of an empire."

The Mexican Federation was transformed into the Sinaloa Cartel in the 2000s.

Guzman and his organization moved drugs with the help of thousands of members, by force and sometimes stealth.

In Tamaulipas, Los Zetas Cartel impeded the Sinaloa's routes.

"With new cartel, with Lazcano and 40, they changed it and they were not permitting them to cross their drugs," explained Fontes. “And, what the Sinaloa cartel would do is use Monterrey, Nuevo Leon as their base. And, they would actually have warehouses where they would store their dope and smuggle the dope without telling the Gulf Cartel and paying any fees.”

Often when discovered operating within Zetas' territory, Sinaloa's drivers were killed and their drugs stolen.

Sinaloa also proved violent. They were behind many killings done to promote prestige, punish disloyalty and failure, and to preserve power. It also expanded to unwilling participants.

"If you look at history when the war between Sinaloa and the Gulf Cartel was happening, one of the terms they used is 'carne para el cañon,'” said the former FBI agent. “Sometimes you would see immigrants at the border, or you would have these large prison breakouts where they needed people to fight for them. And, they would provide them weapons and ammunition, and these people would be foot soldiers without any training.”

Thousands upon thousands disappeared during this time. Crime went unpunished; a system ensured that.

"A cartel leader cannot survive without bribing people, because that's their impunity for them to cross their drugs and operate freely," said Fontes.

‘El Chapo’ was finally arrested. A void was created.

Since then, others have filled the gap.

"Part of the Matamoros and the Reynosa group is fractured. And, I'm aware that one of the two of the Gulf Cartel is favoring ‘Chapo’ and the Sinaloa Cartel, and it's affecting the smuggling of people and drugs. And, the area of McAllen/Reynosa has always been a favorite spot," Fontes believes.

He said these splinter groups will continue to cause strife for those living in the Matamoros and Reynosa communities.