On Monday, an abandoned truck on the outskirts of San Antonio, Texas, was found on the side of a desolate road.  Responders discovered a tragedy: dozens of migrants, trapped in the back of the truck in deadly heat.  The death toll is now over 50 people, with several survivors still in hospitals fighting for their lives.

We speak with Jason De León, professor of anthropology at UCLA and director of the Undocumented Migration Project, who studies clandestine border crossings, about how and why tragedies like this happen.