On a dusty, remote ranch across the Rio Grande from this Texas border town, an intimidating drug lord stood over 13-year-old Rosalio Reta and handed him a gun.
Reta didn't know who the man was, but it was clear he instilled fear and commanded respect among everyone standing around watching the dramatic scene unfold.
The American teen had never before met anyone who carried a pistol adorned with such an unforgettable decoration: the number "40" encrusted in diamonds on the handle.
The cartel leader looked at Reta and ordered him to shoot and kill a man tied up on the ground. If he refused to murder the stranger, Reta recalls, the drug lord would have killed him.
Rosalio Reta's career as a teen drug cartel assassin had begun.
"I knew that my life had just changed forever," Reta told CNN this week, 11 years later. "That's a day that I'm never going to be able to forget. After that, I didn't have no life."
Reta's boyhood friend Gabriel Cardona says he started his life as a criminal by stealing cars and selling them across the border in Mexico. He graduated to smuggling drugs and weapons across the Rio Grande. Cardona says it wasn't long before he also became a drug cartel assassin. He was only 16.
Reta and Cardona agreed to give CNN rare interviews from the Texas prisons where both men are serving life sentences for murder. They offered a first-hand glimpse inside the sinister world of drug cartels, a world that plagues innocent people on both sides of the border.
The mysterious drug lord who ordered Reta to shoot the stranger at the ranch that day, Reta says, was Miguel Angel Trevino. For years, Trevino was the unrivaled leader of the ruthless Zetas drug cartel until police arrested him last month just outside Nuevo Laredo, Mexico.
Trevino, 40, faces charges of organized crime, homicide, torture and money laundering, a Mexican government security spokesman told CNN in July. There were at least seven warrants for his arrest.
Many Zeta leaders often use numbers as their cartel nicknames. On the streets of Mexico, Trevino was known as "Z-40."
One of the most feared and powerful drug kingpins in the world, Trevino took drug cartel brutality to never-before-seen levels. Mexican and United States law enforcement agencies accuse Trevino of killing hundreds of people while laundering hundreds of millions of dollars.
Although Z-40 virtually ruled northern Mexico without fear, as Reta came to know him he began to see Trevino as a regular guy. Reta watched others respond to Trevino's tough leadership.
Trevino had built control and protection systems to insulate his organization at every level from law enforcement agencies and politicians. To make a point, sometimes Trevino sent messages along with decapitated corpses of rival cartel members, said Reta.
"Absolute control," Reta said of Trevino's power. "In a gun battle, in a confrontation, he's the first one to get out of his truck and lead his people. He's not going to ask people to do something that he's not willing to do himself. That's why a lot of people follow him."
Entering the narco world 'lifestyle'
Reta, 24, and Cardona, 26, still bear signs of their years as feared assassins.
Reta has bizarre markings around his eyes; Cardona has drawings of eyeballs tattooed on his eyelids. A large image of "Santa Muerte" -- or Saint of Death -- marks Cardona's back. Denounced by Mexico's Catholic Church, Santa Muerte is a popular symbol among drug traffickers.
CNN was first to broadcast the police interrogation videos from which the world first learned about Reta and Cardona, sparking worldwide fascination with both men and making them infamous legends of a narco world.
Cardona and Reta grew up on Lincoln Street in Laredo, just a few blocks from the city's largest border crossing checkpoint.
Over the years the ramshackle neighborhood has developed into a discarded border region where homes sit on dilapidated foundations and families live under crumbling rooftops.
Reta was one of 10 children and Cardona was one of five boys whose father disappeared early in his life.
"On the border, a lot of people get dragged into this lifestyle," Reta said. "But what we fail to see is that we do it to ourselves."
Reta was a young boy headed down the wrong path. He had followed two friends to the ranch across the border where he was ordered to kill for the first time. The friends were mingling with questionable characters but he was "curious" about the narco world. When Reta arrived at the ranch, it was a crash course in drug cartel culture.
"They were torturing people and getting information from them," said Reta. "I couldn't believe what I was seeing. People getting tortured, killed, decapitated. It was kind of hard to believe."