SAN ANTONIO >> The driver of a semitrailer found outside a San Antonio Walmart in July packed with immigrants, including 10 who died, faces additional charges in the smuggling case and another defendant has now been charged, federal officials said today.

The U.S. attorney’s office in San Antonio said a grand jury returned the seven-count superseding indictment this afternoon. U.S. Attorney Richard Durbin Jr. said in a filing that he won’t seek the death penalty against the driver, James Bradley Jr., 60.

Prosecutors said the indictment also alleges Pedro Silva Segura, 47, of Laredo, who is in the U.S. illegally, transported immigrants and tried to shield them from detection. He could face up to life in prison or death penalty.

The indictment charges Bradley and Silva each with one count of conspiracy to transport and harbor immigrants who are illegally in the U.S. for financial gain resulting in death; one count of conspiracy to transport and harbor immigrants who are illegally in the U.S. for financial gain resulting in serious bodily injury and placing lives in jeopardy; and two counts of transporting immigrants who are illegally in the U.S. resulting in serious bodily injury and placing lives in jeopardy.

The superseding indictment also charges Bradley alone with the three additional counts: transportation of immigrants who are illegally in the U.S. resulting in death; transporting immigrants who are illegally in the U.S. resulting in serious bodily injury and placing lives in jeopardy; and possession of a firearm by a convicted felon.

Bradley could get up to life in prison. Silva faces up to life in prison or the death penalty.

According to court documents, police officers responding to the Walmart on July 23 found people standing and lying in the rear of the trailer and Bradley in the cab.

At least 39 people had been packed inside the semitrailer, most of them Mexicans who had crossed the United States’ southern border. The trailer’s cooling system was broken, and witnesses told authorities and The Associated Press that they fought to breathe and tried in vain to get the trailer to stop as it headed north.

Eight people were found dead inside, and another two died after being hospitalized.

Court records said the immigrants estimated the trailer contained between 70 and 180 to 200 people during transport. They also described differing fees for being transported. Authorities also recovered a .38 caliber pistol from inside the cab.

Bradley, who was arrested at the scene, has remained in federal custody. Kimberly Stevens, one of his attorneys, had no comment today on the superseding indictment.

According to a criminal complaint released in July, Bradley denied knowing anyone was inside the trailer. He told investigators that the trailer had been sold and he was transporting it for his boss from Iowa to Brownsville, Texas. But he said he had driven to Laredo, Texas, and stopped twice there before driving back to San Antonio, in the opposite direction from Brownsville.

Silva is in custody and awaiting transfer to San Antonio for his initial appearance in federal court, which has not yet been scheduled. It was unclear if he had an attorney.

Authorities have said they are investigating the case as part of a broader operation to organize and fund the movement of people illegally across the United States’ southern border.