When Dan Johnstone and Castor Fernandez decided to make “Cowboy Cartel,” their 4-part documentary on the incredible but true take-down of Mexico’s notorious Los Zetas cartel, they knew one thing for sure.

“It’s such an unbelievable story but we never wanted to make a story about violence.” Johnstone said in a joint Zoom interview with his co-director. “It’s very difficult to tell a story about a cartel without the violence but this was an amazing way to deepen and make that story much more complex.”

“We went in knowing it’s not about violence,” Fernandez added. “You already know about the violence. If you Google ‘the most deadly violent cartel,’ a lot comes up. We don’t need to tell that story.”

What “Cowboy Cartel” tells is a mighty David versus Goliath tale of how rookie FBI agent Scott Lawson grabbed a link that he saw as a way in and just would not let it go. His investigation ultimately took down the Treviño brothers, leaders of Mexico’s powerful Los Zetas cartel.

As the Treviños terrorized thousands with their power, money and influence, Lawson risked his life on a hunch: tracking the brother’s racehorse transactions in the United States, which meant infiltrating the deadly cartel to uncover their international money laundering operations.

“A lot of people’s understanding, rightfully so, stops at that violence, because it is pervasive, horrific and affects people’s lives,” Johnstone noted. “We tell a story where we can say, ‘You think you know. You don’t know the story.’

“This is about financial crime. It’s about seeing the sophistication, the complexity of how institutions and systems that we have in America, that we are proud of, get used for nefarious means by very sophisticated people doing nefarious things. That is an opportunity.”

“Cowboy Cartel” is also, he said, “A story about belief. Scott wasn’t believed in what he was doing. He believed in his hunch.

“Scott was a rookie FBI agent with less than a month on the beat! He really, honestly, probably had no business moving the way he did. But he knew in his gut that what he was doing was right.

“They would neigh at him as he walked through the office. He got the nickname Mr. Ed because everyone thought he was just chasing his tail and embarrassing himself and the agency.

“But through perseverance and just guts, he proved everyone wrong and did the impossible.”

Now that they’ve told the story in this documentary, is it a public saga that anyone can adapt? Or do they need your consent?

“They need to come to us,” Johnstone answered with a smile, “because we would tell the best story.”

Scott Lawson, FBI Agent, in “Cowboy Cartel,” premiering Aug. 2 on Apple TV+.(Photo Apple TV+)