But the young migrants from across Latin America insisted on going. They met their ends together, among 72 migrants massacred just 100 miles (160 kilometers) from the U.S. border.

Pieces of the migrants’ lives – and the story of their terrible fate – are slowly emerging as investigators painstakingly work to identify the bodies, which were discovered bound, blindfolded and lying in a row after what appears to be Mexico’s worst drug-cartel massacre.

The survivor, 18-year-old Luis Freddy Lala Pomavilla of Ecuador, said the killers identified themselves as Zetas, a group begun by former Mexican army special forces soldiers and now a lethal drug gang that has taken to extorting migrants.

The Zetas control much of the northern state of Tamaulipas, cattle-ranching country that is the last leg for migrants running the gantlet up Mexico’s east coast to reach Texas.

Mexico’s drug gangs have long kidnapped migrants and demanded payment to cross their territory. But the Mexican government says the cartels are increasingly trying to force vulnerable migrants into drug trafficking, a concern also expressed by U.S. politicians demanding more security at the border.

Lala, who is recovering from a gunshot wound to the neck and is under heavy guard, told investigators the migrants were intercepted on a highway by five cars, according to his statement that The Associated Press had access to Friday.

More than 10 gunmen jumped out and identified themselves as Zetas, Lala said. They tied up the migrants and took them to the ranch, where they demanded the migrants work for the gang. When most refused, they were blindfolded, ordered to lie down and shot.

Lala’s mother, who lives in the United States with her husband, said she spoke to her son Friday for the first time since the attack. She said she had been trying to reach him since he didn’t arrive at their home as scheduled.

“Every afternoon, I was buying phone cards to call the coyote (smuggler) and find out where my son is,” she said. “I did nothing but call and call and call, and there was never an answer.”

Then a Mexican hospital worker phoned and told them their son had been in “an accident.”

The AP is not using the woman’s name or her location to avoid putting her in potential danger.