At least nine people were found dead early Sunday morning inside a tractor trailer in a parking lot of a Walmart in San Antonio, in what police have called a "horrific tragedy."
All nine victims were adult males, authorities said.
A tenth individual later died at the hospital after being rescued from the trailer, a spokesman for the US Attorney in the Western District of Texas, confirmed to BuzzFeed News on Monday.
The 60-year-old driver of the truck, James Matthew Bradley Jr., from Clearwater, Florida, was charged with one count of transporting undocumented immigrants, United States Attorney Richard L. Durbin, Jr., announced Monday.
A federal complaint filed Monday alleged that Bradley unlawfully transported immigrants in violation of law, resulting in the death of 10 of the individuals who were transported. If convicted, Bradley faces a sentence of life imprisonment or death, a $250,000 fine, and three years of supervised release.
Bradley appeared in court in Monday morning.
"We're looking at a human-trafficking crime this evening," San Antonio Police Chief William McManus said at press conference in the early hours of Sunday morning.
McManus said that a Walmart employee called police after an individual from the truck approached to ask for water.
Police believe the deaths were caused by asphyxiation and heat exposure, according to a statement.
At least 39 people — including at least two "school-aged children" were recovered from the trailer, authorities said. One of them was found in a wooded area near the tractor trailer. The others were being treated at area hospitals.
San Antonio Fire Chief Charles Hood said that many of them had heart rates above 130 and were "hot to the touch."
Temperatures in San Antonio on Saturday hit 100 degrees, according to data from the National Weather Service.
"These people were in that trailer without any signs of water so you're looking at a lot of heat stroke, dehydration," Hood said, adding that the air conditioner in the vehicle was not working.
"We're very fortunate that there weren't 38 of these people that were all locked inside of this vehicle dead," Hood said.
"This tragedy demonstrates the brutality of the network of which I often speak," said US Secretary of Homeland Security, John F. Kelly, in a statement. "These smugglers have no regard for human life and seek only profits. The Department of Homeland Security and its partners in the U.S., Mexico and Central America will continue to root out these smugglers, bring them to justice and dismantle their networks," Kelly said.
Richard Durbin Jr., US Attorney in the Western District of Texas, called the incident a "smuggling venture gone horribly wrong," in a statement.
"All were victims of ruthless human smugglers indifferent to the well-being of their fragile cargo," Durbin said. "Imagine their suffering, trapped in a stifling trailer in 100-plus-degree heat," he added, saying that his office, along with the local and federal authorities, would "identify those who were responsible for this tragedy."
Many more people may have originally been in the tractor trailer. Surveillance video from the parking lot appeared to show vehicles arriving at the parking lot to pick up passengers who had survived.
Authorities are looking into where the truck came from, and how long it had been at the Walmart.
"This is not an isolated incident. This happens quite frequently," McManus said. "Fortunately, we came across this one. Fortunately, there are people who survived."