A 60-year-old Clearwater man has been charged in the Texas human trafficking case that has left 10 people dead. 

James Bradley Jr., 60, of Clearwater, appeared in federal court on charges of illegally transporting immigrants for financial gain, resulting in death. He was ordered held for another hearing on Thursday.

He could face the death penalty.

Authorities on Saturday found eight bodies inside the crowded 18-wheeler parked in the San Antonio summer heat late Saturday, and two more victims died at a hospital, victims of what officials said was an immigrant-smuggling attempt gone wrong.

"We're looking at a human-trafficking crime," San Antonio Police Chief William McManus said Sunday, calling it "a horrific tragedy."

Authorities discovered eight bodies inside the crowded 18-wheeler parked in the summer heat, and two more victims died at a hospital. Officials feared the death toll could rise because almost 20 others rescued from the truck were in dire condition, many suffering from extreme dehydration and heatstroke.

A passenger told authorities that people took turns breathing through a hole in the trailer and pounded on the walls to try to get the driver's attention, according to court papers.

Authorities would not say whether the trailer was locked when they arrived, but they said it had no working air conditioning.

The victims "were very hot to the touch. So these people were in this trailer without any signs of any type of water," Fire Chief Charles Hood said.

Based on initial interviews with survivors of the San Antonio tragedy, more than 100 people may have been packed into the back of the 18-wheeler at one point in its journey, Immigration and Customs Enforcement acting Director Thomas Homan said. Officials said 39 people were inside when rescuers arrived, and the rest were thought to have escaped or hitched rides to their next destination.

Four survivors appeared to be between 10 and 17 years old, Homan said. Investigators gave no details on where the rig began its journey or where it was headed.

Mexican Consul General in San Antonio Reyna Torres said Mexican nationals were among the survivors and those who died on the rig. The Mexican government also released a statement Sunday night expressing its condolences to the relatives of those who died and called for an "exhaustive investigation."

A Guatemalan official said two natives of Central American country were among those hospitalized. Consul Cristy Andrino in McAllen, Texas, said the two told her they had crossed into the U.S. on foot and were later picked up by the rig.

But Homan said it was unlikely the truck was used to carry the immigrants across the border into the United States. He said people from Latin America who rely on smuggling networks typically cross the border on foot and are then picked up by a driver.

"Even though they have the driver in custody, I can guarantee you there's going to be many more people we're looking for to prosecute," Homan said.

Who is James Mathew Bradley Jr.?

Bradley is a bit of a ghost as far as any records tied to his past. 

No criminal record for Bradley has been found in the state of Florida. Also, no confirmed social media accounts have been located, and no family members for Bradley were found. 

Bradley was charged Monday in the deaths of 10 of his passengers.

The U.S. Homeland Security Department stepped in to take the lead in the investigation from San Antonio Police. DHS Secretary John Kelly said the incident demonstrates the brutality of smuggling organizations that "have no regard for human life and seek only profits."

The truck had an Iowa license plate and was registered to Pyle Transportation Inc. of Schaller, Iowa. A company official did not immediately respond to a phone message seeking comment.

San Antonio is about a 150-mile drive from the Mexican border. The temperature in San Antonio reached 101 degrees Saturday and didn't dip below 90 degrees until after 10 p.m.

The tragedy came to light after a person from the truck approached a Walmart employee and asked for water late Saturday night, said McManus, the local police chief.

The employee gave the person water and then called police, who found the dead and desperate inside the rig. Some of those in the truck ran into the woods, McManus said.

Investigators checked store surveillance video, which showed vehicles arriving and picking up people from the truck, authorities said. Walmart released a brief statement Sunday saying it was doing what it could to help investigators.

On Sunday evening, about 100 people gathered at a San Antonio church for a vigil to mourn those killed.

Previous case

It was just the latest smuggling-by-truck operation to end in tragedy. In one of the worst cases on record in the U.S., 19 immigrants locked inside a stifling rig died in Victoria, Texas, in 2003.

In the May 2003 case, the immigrants were being taken from South Texas to Houston. Prosecutors said the driver heard them begging and screaming for their lives but refused to free them. The driver was sentenced to nearly 34 years in prison.

The Border Patrol has reported at least four truck seizures this month in and around Laredo, Texas. On July 7, agents found 72 people crammed into a truck with no means of escape, the agency said. They were from Mexico, Ecuador, Guatemala and El Salvador.

Authorities in Mexico have also made a number of similar discoveries over the years. Last December, they found 110 migrants trapped and suffocating inside a truck in the state of Veracruz. Last October, also in Veracruz state, four migrants suffocated in a truck carrying 55 people.

Information from the Associated Press was used in this report.