Nine people are reportedly dead and at least 17 are in critical condition after a tractor trailer filled with undocumented immigrants was discovered at the border on a sweltering day.
McManus said events like this are all too common and warned the public to contact police if they see groups of people exiting from large vehicles like tractor-trailers. Thirteen others were taken on Priority 2 status: not immediately life-threatening.
According to court documents, Bradley claims he didn't know anyone was in the truck, telling agents he was surprised when he was "run over by Spanish people and knocked to the ground".More news: Identity Mistake? Released Lucky Whitehead wasn't in VA day of arrest?
"The truck was loaded with people", Chief Hood added.
After the victims have been treated for injuries-two of whom were just 15 years old-they will be turned over the Immigration and Customs Officials.
McManus said the Department of Homeland Security had joined the investigation.
There have been many cases of migrants - often scores at a time - stranded and killed in northern Mexico when the truck they were being transported in was abandoned in heat by drivers.More news: Doctors treating Charlie Gard get death threats
He called the case "a horrific tragedy".
The group included children and adults, the police chief said. The truck lacked air conditioning and water, and 30 other victims had to receive treatment for heat stroke and exhaustion.
Temperatures in San Antonio on Saturday hit 100 degrees, according to data from the National Weather Service. Surveillance video from the parking lot appeared to show vehicles arriving at the parking lot to pick up passengers who had survived. Bradley, who's in custody, and everyone else found to be involved is expected to face state and federal charges as early as Monday.More news: Stunned Yankees react to Aaron Judge homer nearly leaving Safeco Field