The driver of a tractor-trailer packed with people illegally entering the US in an alleged human smuggling operation has been indicted on charges related to the deaths of 10 of those inside.
James Bradley was indicted on Wednesday by a federal grand jury in San Antonio on five counts, including a count of illegally transporting immigrants for financial gain, resulting in death, and a separate count of conspiracy to transport immigrants illegally, resulting in death.
Those charges carry the possibility of the death penalty.
Bradley was also indicted on two counts related to illegally transporting immigrants resulting in serious bodily injury, and one count of firearm possession by a convicted felon.
The indictment alleges Bradley, who pleaded guilty in 1997 to a domestic violence case in Colorado, was in possession of a .38-calibre pistol.
At least 39 people were inside the trailer as it drove from the border city of Laredo to San Antonio, about 150 miles north, last month, ending up in a Walmart store car park.
The trailer's refrigeration system was broken, and investigators said passengers struggled to breathe as the temperature rose to dangerous levels. One witness told The Associated Press he heard people crying and asking for water.
Twenty-two survivors have been released from hospital and are being held in detention as potential witnesses against Bradley. Two survivors remain in hospital.
Four of the survivors testified before the grand jury, said Michael McCrum, a San Antonio lawyer appointed to represent them.
"They came to America wanting just to work, as they could not find a job in Mexico that could support their families. And yet, the circumstances of what happened brought them to this situation," he said.
"They were asked to tell the truth about how they suffered, and they did."
Investigators have said they believe Bradley was part of a broader conspiracy funding and planning the smuggling operation, though they have not announced any additional arrests or charges.
According to a criminal complaint released in July, Bradley told investigators the trailer had been sold and he was transporting it for his boss from Iowa to Brownsville, Texas.
He denied knowing people were inside the trailer. After hearing banging and shaking, he opened the door and was "surprised when he was run over by 'Spanish' people and knocked to the ground," according to the criminal complaint.
Human smuggling operations often linked to Mexican drug cartels are a major problem for law enforcement along the United States' southern border.
Border Patrol agents in West Texas found 20 people crammed in a semitrailer earlier this week, a day after police in the border city of Edinburg discovered 16 people inside another trailer.
Most of the people known to have been on board were from Mexico. Others are believed to have fled from the truck after it stopped.