Defense Secretary Jim Mattis is preparing an order that would send approximately 800 U.S. troops to the border, CBS News' David Martin has confirmed, as President Trump's frustration builds over the caravan of migrants approaching the U.S.  

Investigators believe a border patrol agent who died in West Texas after suffering extensive injuries to his head and body may have fallen down a 14-foot culvert, and his partner, who radioed for help, has no memory of what happened, according to a U.S. official with knowledge of the investigation.