David Aguilar is no stranger to a border crisis.

President George W. Bush tapped him in 2004 to lead the U.S. Border Patrol as the agency wrestled with reining in what was at that point the highest-ever number of illegal border crossers from Mexico into the United States. At that point his 12,000 agents were taking 1.2 million people into custody annually. And that was down by 25% from four years prior. In 2001, 1.6 million unauthorized immigrants were stopped at the border that year, the most since 1925.