It’s not every day you hear the words horse and deadly drug cartel in the same sentence.

A new Apple TV+ docuseries, “Cowboy Cartel,” examines Mexican drug cartel Los Zetas and its takedown led by rookie FBI agent Scott Lawson.

The Zetas were once known as one of the deadliest drug cartels in Mexico, led by brothers Omar Treviño Morales and Miguel Angel Treviño Morales. But then, the four-legged animals got involved.

In January 2010, the FBI’s Laredo, Texas, office received a tip that the Zetas were involved in money laundering operations involving quarter horses on U.S. soil.

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The duo’s other brother, José Treviño Morales, was involved in a shell game of making straw purchases and deals worth millions of dollars to disguise drug money through the sale of quarter horses and race winnings, the U.S. Attorney’s Office for the Western District of Texas said after he was sentenced in 2013.

The scheme included structuring cash deposits in amounts under $10,000 to bypass mandatory bank reporting requirements, officials said.

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The FBI raided José Treviño Morales’ home and stables in Lexington, Okla., on June 12, 2012. (AP)

The hardest part for Lawson and his team in all of this was proving the crime was in fact illegal and doing it before the brothers and the Zetas headed back to Mexico.

The FBI eventually raided José’s home and stables on June 12, 2012. This resulted in the arrest of Miguel in 2013 as well as José, who is currently serving out a 20-year sentence in federal prison.

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José Treviño Morales acknowledges the crowd at the All American Futurity horse race at Ruidoso Downs, N.M., on Sept. 6, 2010.

Most of the other Zetas were also eventually captured and are currently serving time behind bars, though some have spun off into other cartel groups.

For the first time, the four-part series offers interviews with Lawson and other local and national law enforcement agents who assisted in uncovering the brothers’ illegal doings. 

Lawson, a rural Tennessee investigator, infiltrated the deadly cartel to uncover its international money laundering operations. 

“My boss told me, ‘Here, we work against the Zetas,’” said Lawson, who was responsible for breaking the case.

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Law enforcement personnel take a horse away from the stable area at Ruidoso Downs Racetrack and Casino in Ruidoso, N.M., on June 12, 2012. (Ruidoso News/AP)

Lawson also gives insight into other key pieces of information about capturing the brothers and their accomplices, revealing that it took 1,200 law enforcement personnel to come together on the same day for the takedown in the complicated investigation that spanned more than three years.

Others who were involved in the takedown and took part in the series included IRS agent Steve Pennington; Irving police officers Steve Junker, Brian Schutt and Kim Williams; Assistant United States Attorney Doug Gardner; Pulitzer Prize-winning New York Times journalist Ginger Thompson; and Joe Tone, the author of “Bones: Brothers, Horses, Cartels, and the Borderland Dream.”

“Anyone who stood up to them would wind up dead,” one interviewee says.

“Anyone who stood up to them would wind up dead.”

This handout photograph released during a news conference by the Mexican government on July 15, 2013, shows a series of photographs of Miguel Angel Treviño Morales. (Reuters/Secretaria de Gobernacion)

From a 911 call by a special agent who had been shot and attacked on a Texas highway to cars shown going up in flames, experts in the case break down just how the gang used violence to mark its territory.

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“All the cartels use violence to achieve their aims. The Zetas took it to another level,” a law enforcement voice says.

“All the cartels use violence to achieve their aims. The Zetas took it to another level.”

“When you think of the drug cartels, you think of the drugs, you think of the violence, and you think of money,” another person says as footage of masked men holding guns count cash. “But you do not think of horses.”