(NewsNation) — Two men were indicted by a grand jury in San Antonio for the deaths of 53 migrants found dead in a horrifically hot semitrailer in San Antonio during a suspected botched smuggling run.

Homero Zamorano, 46, and Christian Martinez, 28, both of Pasadena, Texas, were indicted on counts of transporting and conspiring to transport migrants illegally resulting in death, and transporting and conspiring to transport migrants illegally resulting in serious injury.

The incident marked the deadliest tragedy ever involving migrants crossing the southern border into the United States.

In sweltering Texas heat, 67 migrants were stuffed into a semitrailer to be taken across the border; 53 of those migrants died from heat and dehydration after the trailer was abandoned near San Antonio on June 27.

“The patients that we saw were hot to the touch, they were suffering from heat stroke, heat exhaustion —no signs of water in the vehicle — it was a refrigerated tractor-trailer but there was no visible working AC unit on that rig,” San Antonio Fire Department Chief Charles Hood said.

Arriving police officers detained Zamorano after spotting him hiding in some nearby brush, according to a statement from the U.S. Attorney’s Office. A search of Zamorano’s cellphone revealed calls with Martinez concerning the smuggling run.

Surveillance video of the 18-wheeler passing through a Border Patrol checkpoint showed the driver matched Zamorano’s description, according to the indictment. One survivor of the journey, a 20-year-old from Guatemala, told The Associated Press that smugglers had covered the trailer’s floor with what she believes was powdered chicken bouillon, apparently to throw off any dogs at the checkpoint.

Ten of the victims were teenagers, and the dead hailed from Mexico, Honduras, Guatemala and El Salvador.

The Associated Press contributed to this report.