(NewsNation) — In the moments when authorities discovered dozens of migrants dead inside a sweltering tractor-trailer in Texas, an immigration official says the truck’s driver tried to escape law enforcement by pretending to be one of the survivors.

The Texas man accused of driving the tractor-trailer, Homero Zamorano Jr., 45, appeared in federal court Thursday. He is charged with smuggling resulting in death.

The initial court appearance in the case lasted just minutes, with Zamorano giving simple answers to the judge about the charges against him and his rights. The judge also appointed Zamorano a federal public defender and a second attorney.

According to reports, 73 people were packed inside the scorching big rig when it was found along the edge of San Antonio on Monday. Of the 73 people, 53 died, making the tragedy the nation’s deadliest smuggling incident on the U.S.-Mexico border.

Mexico’s National Immigration Institute says at least 27 of the victims were from Mexico, 14 from Honduras, seven from Guatemala and two from El Salvador.

Authorities are not sure on the time or location of where the migrants got on the truck headed to San Antonio, but investigators think it may have been near Laredo, Texas. The tractor-trailer did pass through an inland U.S. Border Patrol checkpoint on Interstate 35. The checkpoint is on a busy highway roughly 25 miles north of Laredo. Now, Texas Gov. Greg Abbott said troopers would set up more truck checkpoints on highways.

Robert Almonte, a former U.S. marshal in the Western District of Texas and a cartel expert, joined NewsNation’s “Rush Hour” to speak about the migrant truck tragedy.

Almonte says cartels have become even more involved in human smuggling due to the surge of migrants trying to make it across the border. Based on what Almonte knows about Zamorano, he believes possibly one of three cartels hired him to carry out the smuggling attempt.

“The area where this guy came from with Laredo, Texas, and San Antonio, the connection is going to be the Interstate 35. In Nuevo Laredo, the main cartel operating there is the CDN cartel. You also have the Gulf Cartel there, and then also the new generation cartel. So it could have been any one of those three cartels involved. But that’s the main area for the cartels and the CDN cartel. So they use different techniques to recruit and then say, ‘Hey, you want to make some money? Drive these people to a certain destination and, and we’ll pay you a lot of money’ and no doubt this person was going to be paid a lot of money,” Almonte explained.

Acting Special Agent in Charge of Homeland Security Investigations Craig Larabee says migrants sometimes pay anywhere from $8,000 to $10,000 to be moved across the border, placed in a tractor-trailer and taken to San Antonio, then transferred into smaller cars to reach their destinations within the U.S.

Almonte thinks Zamorano had the cartel connection in place and had smuggled humans for them before, gaining their trust.

“That’s probably why the cartel trusted him with so many migrants, because he’d done it before. There’s no doubt in my mind, he’d done it before,” Almonte explained. “Then unfortunately, this one turned out to be a deadly trip for those migrants.”

The smuggling charge Zamorano faces carries a possible death sentence. A hearing to discuss bail eligibility for Zamorano is scheduled for next week.

Christian Martinez, 28, also faces charges linked to the smuggling incident. He is accused of conspiracy and communicating with Zamorano about transporting the migrants. Two other men from Mexico are also in custody.

The Associated Press contributed to this report.