This information was revealed to a police informant by an alleged co-conspirator, Christian Martinez.
According to the US Department of Justice, the 28-year-old had communicated by text message with the driver of the vehicle, Homero Zamorano Jr., in the hours before and after the grisly discovery.
Where are you ? reads the transcript of a message from Martinez to Zamorano sent at 1:40 p.m. Monday, as authorities were removing dozens of bodies from the trailer.
Martinez then sent several more messages, including a final one at around 6:15 p.m., says the New York Post. That’s when authorities discovered Zamarono near the truck, hiding in the brush. Mexican authorities say he was trying to pass himself off as a survivor.
According to Reuters, the informant claims to have spoken to Martinez after the incident. The latter reported to him that
the driver was unaware that the air conditioning unit had stopped working and caused the death of these people.
Addicted to methamphetamine
Law enforcement sources claimed the driver was under the influence of methamphetamine at the time they encountered him.
Officers made his arrest when surveillance photos showed him driving the truck passing a US border checkpoint in Laredo, Texas.
Homero Zamorano Jr and Christian Martinez are both charged with smuggling of migrants causing death, a crime punishable by death.
The two men are part of a group of four people charged in connection with the investigation into the deadliest episode of human trafficking in US history.
Investigators were able to trace the registration of the vehicle to an address in San Antonio which they put under surveillance, reports the New York Post.
Two Mexican nationals, Juan Claudio D’Luna Mendez, 23, and Juan Francisco D’Luna Bilbao, 48, were arrested at the scene and face charges of unlawful possession of firearms.
Their involvement in the tragedy has not been specified.
A mechanical breakdown
Authorities suspect the 64 migrants boarded on the US side of the border with Mexico. They would then have been left in the back of the trailer without air conditioning after a mechanical failure.
The mercury reached 39.4 degrees Celsius that day in San Antonio.
Among the victims are 27 Mexican citizens, as well as 14 Hondurans, seven Guatemalans and two Salvadorans.
At least 40 men and 13 women died and another 11 migrants were hospitalized with heat-related issues. Other minor migrants remain hospitalized.
The UN estimates that at least 650 migrants died last year trying to reach the United States.
Mexican authorities report that another truck carrying a group of migrants rammed a trailer after it escaped a U.S. Customs and Border Protection checkpoint in the town of Encinal, Texas on Thursday.
The accident killed four people and injured three.