A photo showing a young girl at the U.S.-Mexico border, crying as an officer searched her mother, has gone viral.

In a recent six-week period there were nearly 2,000 family separations following a crackdown on illegal border crossings.

What's the story behind the photo? Pulitzer-winning photographer John Moore says he had to pause after taking it.

(Photo: A two-year-old Honduran asylum seeker cries as her mother is searched and detained near the U.S.-Mexico border. Credit: John Moore/Getty Images)