Former Cartel del Golfo Leader and Cooperating Witness In Case Against 'El Menchito' Dies While In U.S. Custody

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Mario Ramírez Treviño, a former leader of the Cártel del Golfo (Gulf Cartel), was confirmed dead by the U.S. Department of Justice on March 21. He had spent nearly eight years in a U.S. prison awaiting the resolution of his trial.

Known as "El Pelón" or "X20," Treviño took command of the cartel in 2013 following the murder of David Salgado, alias "Metro 4." He led the group for a short time before being arrested by Mexican authorities in August 2013. After spending nearly four years in a Mexican prison, he was extradited to the U.S. in 2017 on charges of money laundering and drug trafficking.

Mexican media outlets reported that Treviño died while in custody at a federal prison. According to a document shared by Marlon Cobar, Chief of the Narcotic and Dangerous Drug Section (NDDS) — a division within the Justice Department tasked with enforcing laws related to the control, regulation, and prevention of the illegal use, trafficking, and abuse of narcotics and dangerous drugs — authorities confirmed that "El Pelón" passed away on March 13. However, the exact cause of death, as well as the circumstances surrounding his passing, have not yet been disclosed.

U.S. prosecutors have requested to cancel his pending sentencing hearing and dismiss the criminal charges he faced since being extradited to the U.S. in 2017.

At the time of his extradition, Treviño and 25 others faced an indictment on three counts of conspiracy to manufacture and distribute at least five kilograms of cocaine and one ton of marijuana. He was also charged with two additional counts of attempted distribution for his alleged involvement in a 10-ton cocaine shipment seized by Mexican authorities in October 2007 and another shipment of over two tons confiscated in Panama in November of the same year.

Prosecutors alleged that Treviño led the Gulf Cartel with the help of Los Zetas. Both criminal groups worked together in an alliance known as "La Compañía" which distributed drug shipments from Colombia to the U.S.

During the almost eight years he was behind bars in an U.S. prison, Treviño served as a cooperating witness in drug trafficking cases involving other drug lords. Just last year he testified against Rubén Oseguera González, alias "El Menchito," the son of Nemesio Oseguera Cervantes, "El Mencho," leader of the Cártel Jalisco Nueva Generación (CJNG).

During his testimony, he recounted meeting "El Menchito" in 2014 while they were both incarcerated at the Altiplano prison. Treviño claimed that Oseguera González asked for his help to acquire firearms and to arrange a cocaine purchase for his father.

The testimony given by "El Pelón" was used by prosecutors as part of the evidence used against Oseguera González who was later found guilty of drug trafficking and firearm possession. "El Menchito" was sentenced to life in prison plus an additional 30 years earlier this month.