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A former Mexican drug trafficker who once claimed he was a double agent for the Drug Enforcement Administration took center stage on Thursday against infamous kingpin Joaquin “El Chapo” Guzman at a U.S. trial.

Vicente Zambada became the latest in a parade of cooperators to testify as government witnesses in the conspiracy case against Guzman in federal court in Brooklyn. Like the others, he described the rampant violence and greed that accompanied Guzman’s rise to power atop the Sinaloa cartel.

Lawyers for Guzman — who was sent to the United States in 2017 after gaining notoriety for twice escaping Mexican jails — have sought to portray the cooperators as shady opportunists willing to exaggerate their client’s involvement in the drug trade to earn breaks in their own cases.

Zambada, 43, is the son of Ismael “El Mayo” Zambada, another cartel boss who’s still at large. His uncle, former cartel member Jesus Zambada, has also testified at Guzman’s trial.

Vicente Zambada told the jury Thursday about a meeting in the early 1990s at which a rival drug gang leader told him he wanted to kill his father and Guzman to avenge a botched hit. At another meeting in the mid-2000s, representatives from corrupt Mexican politicians asked if the cartel could help them ship 100 tons of cocaine in an oil tanker ship, he said.

“They wanted to know if my dad and Chapo could provide that amount of coke,” he said.

Zambada said he was arrested before he learned whether the shipment ever occurred.

After Zambada was extradited to the U.S., his lawyers claimed he had been working for the DEA as a confidential informant even as he was smuggling cocaine. In exchange for inside information on the cartel, he had been promised immunity from prosecution, they said.

Prosecutors denied Zambada’s allegation that there was an immunity deal that was “approved at the highest levels of government.” He later pleaded guilty and agreed to cooperate.

Zambada was to retake the witness stand Friday. The trial, which began in mid-November, is expected to continue into next month.