On Monday, the driver of the semi-truck carrying at least 39 immigrants, James Matthew Bradley, Jr., was charged with one count of transporting illegal aliens.

A federal complaint filed Monday morning alleged that Bradley unlawfully transported undocumented immigrants in violation of law, resulting in the death of 10 of the people transported.

Upon conviction, the offense is punishable by life imprisonment or death, a $250,000 fine, and three years of supervised release, according to the U.S. Attorney Richard L. Durbin, Jr.

The apparent smuggling operation involving undocumented immigrants came to a tragic conclusion early Sunday morning when emergency responders found dozens of people in distress inside a hot semi-trailer at a Walmart in southwest San Antonio.

The death toll has risen to 10. Eight people were dead at the scene early Sunday morning. One more died during the day at a San Antonio hospital.

The deceased were reportedly all adult males, according to the Department of Justice United States Attorney’s Office Western District of Texas.

The Mexican Consulate of San Antonio is reporting that 25 of the 39 individuals found in the back of a hot truck Sunday were from Mexico.

Out of the 10 deceased, four are reportedly of Mexican nationality.

Out of the 29 hospitalized, 21 are Mexican, two are third country nationals, and six have not yet confirmed their nationality.

On Monday morning, the U.S. Attorney's office confirmed a tenth victim died in the hospital.

Thomas Homan, acting director of U.S. Immigration and Customs Enforcement, said there may have been more than 100 people in the truck. Only 39 were found inside the trailer and one in the wooded area nearby. Officials believe the rest left the scene.

Four of the passengers are believed to be between 10 and 17 years old, and at least one of them is in serious condition.

San Antonio Fire Department Chief Charles Hood reported that 17 people were transported to hospitals with life-threatening injuries, two of whom has since died, and another 13 had non-life-threatening injuries.

As of Monday, University Hospital confirmed five adult patients, four men and one woman, with heat-related illnesses remain in their care. The hospital said their conditions range from good to critical. A total of seven adults were treated and two were discharged on Sunday.

Early Sunday morning, an employee at the Walmart encountered a person who was disoriented and asking for water, San Antonio Police Chief William McManus said. The person said that there were people who needed help inside the trailer outside the store, which is located at I-35 and Highway 16 on the city's southwest side.

When police arrived on the scene around 12:30 a.m. Sunday, they detained the driver immediately. The United States Attorney's Officer identified the driver as 60-year-old James Matthew Bradley Jr. of Clearwater, Florida. Bradley is being held in federal custody in connection with this incident.

Officials searched the trailer to find several people in various stages of medical distress. At least 29 fire units and two AirLIFE choppers responded to the scene to take care of the victims.

Nicole Perez, who lives behind the Walmart off Fairmeadows Street, watched the scene unfold through her back window.

"It was maybe 1:30 and we heard back to back cops, ambulances, fire trucks, helicopter," said Perez. "We came outside and the helicopter was going around in circles."

Norma Ogden lives across I-35 and woke up to the sirens.

"The sirens just kept going and going. It was nonstop. I thought to myself, this is something really bad," said Ogden.

The 17 victims with life-threatening injuries were taken to University Hospital and San Antonio Military Medical Center. The 13 victims with non-life threatening injuries were taken to five other area hospitals.

Officials said the eight found dead in the truck are believed to have died as a result of heat exposure/asphyxiation. Their bodies were taken to the Bexar County Medical Examiner's Office to be examined so a cause of death can be determined. The Attorney's Office said all of the deceased were adult male.

McManus called the incident a "horrific tragedy." He said store surveillance video showed a number of vehicles arriving at the parking lot and picking up people who had been in the trailer. Police were working to identify those vehicles.

McManus said the trailer appeared to be a smuggling operation. He said the people in the trailer would be reviewed by ICE agents to determine their immigration status. Also, it was announced later Sunday morning that the Department of Homeland Security was taking the lead on the investigation of the incident.

Facebook Live from the scene

The San Antonio Fire Department released the following statement:

"Shortly after 12:30AM (Central) the San Antonio Fire Department responded to 8358 IH-35 S. for a report of multiple people in the trailer portion of an 18 wheeler. First arriving units found a number of people in the back of this trailer all in varying degrees of medical distress. A total of 8 individuals were deceased upon our arrival. 17 patients were transported priority 1 (life threatening injury / illness) and 13 were transported priority 2 (not immediately life threatening). Air ambulances (AirLife), and the SAFD Ambus (mobile mass casualty transportation vehicle) were also both utilized to transport the multitude of patients we encountered. A search of the surrounding area was also conducted to attempt to locate any patients that may have attempted to flee the scene. An additional search will be conducted later this morning once the sun has risen. All questions relating to the potential criminal aspect of this should be directed to the San Antonio Police Department."

Richard L. Durbin, Jr. United States Attorney, Western District of Texas released the following statement:

"San Antonio firefighters and police responded to a horrific scene this morning on the southwest side of town. They discovered an alien smuggling venture gone horribly wrong. Eight immigrants were found dead. At least twenty more were in serious condition. All were victims of ruthless human smugglers indifferent to the well-being of their fragile cargo.

The South Texas heat is punishing this time of year. These people were helpless in the hands of their transporters. Imagine their suffering, trapped in a stifling trailer in 100-plus degree heat. The driver is in custody and will be charged. We will work with the Homeland Security Investigations and the local responders to identify those who were responsible for this tragedy."

San Antonio Mayor Ron Nirenberg released the following statement:

“We are still learning about the tragic events that unfolded on our doorstep overnight, which shines a bright light on the plight of immigrants looking for a better life and victims of human trafficking. As we work to coordinate a humanitarian and legal response to this terrible tragedy, I find comfort in the compassionate response of our first-responders, our local medical professionals and the outpouring of support from our community. I want to thank the Wal-Mart employee who provided water and called 911, an act that helped us prevent more deaths.

We will continue to work closely with local groups and federal agencies to offer support to the survivors and connect them with their families. Our thoughts and prayers go out to everyone who was impacted by this terrible loss of life. Our response should serve as a lesson to the world that San Antonio will not turn its back on any man, woman or child in need.”

Walmart released the following statement:

“This is a very sad situation, and we are doing everything we can to assist the authorities.”

Homeland Security is leading the criminal investigation. The driver faces both state and federal charges, police said.