We are in the visitation room of the maximum-security Telford Unit in East Texas. Not far from where we sit, inmates are working in the fields, making 10 cents a day. For the rest of his life, barring some kind of miracle, this will be Cardona's home. "Prison is hard. It's not what I thought," he says. A sadness settles on him; he lowers his head and slowly blinks. Tattooed on his eyelids, in crude ink, is another set of eyeballs. They are lifeless and wide, and devoid of emotion. When he sleeps, or when his mind drifts to the killing he has seen and done, to the bodies he has burned and buried and hacked to pieces, these eyes look out on the world.

Today, his real eyes exude weariness, which is what you might expect in a kid who triggered one of the largest investigations into Mexican drug-related violence the United States has ever conducted. In a span of 10 months, Cardona and two other American teens killed at least seven people in Texas and Mexico. The one who began killing at 13 would eventually confess to 30 murders. Criminal cases against their co-conspirators are now winding their way through the federal courts. They offer the first look inside the operations of Los Zetas.

A secretive band of bounty hunters, the Zetas were founded in part by a group of soldiers who defected from the Mexican army in the late 1990s and joined the Gulf Cartel, one of three major drug-trafficking syndicates in Mexico. They also may have received training from the U.S. military, the DEA, and the FBI. In time, the Zetas changed the way drug-trafficking organizations in Mexico use violence. Intimidation turned into terror. Like Colombia before it, Mexico has become a place where government is powerless. Kidnappings, carjackings, and assassinations of elected officials are regular occurrences. Thanks largely to the Zetas, whose tactics have been mimicked by other organized-crime syndicates, Mexico stands on the brink of chaos. And kids have become assassins for hire. '"I'm not going to say I haven't killed people, because I have," Cardona says. "But a lot of the stuff they say, it isn't true. They consider me the leader and the organizer, but really, only I know the truth."

THE BOY GREW UP IN LA AZTECA, A BARRIO ON THE BORDER IN DOWNTOWN LAREDO WHERE THE crumbling streets are so narrow that most are one-way and where many of the houses are built of sandstone. It is a neighborhood of grinding poverty. Laundry dries on fence lines, thick oaks and saplings cast long shadows, and lookouts, known in the Mexican underworld as "hawks," watch strangers pass in the night from rooms illuminated by candlelight. "We didnít have anything," Cardona says. "My father, he would beat my mother, and he would beat me and my brother. We grew up with strict rules, and if we did something wrong, my mother would beat us too." "We spanked him all the time," she admits, "when he was a little boy."