Kim Kyung-Hoon/Reuters

A mother and her girls tried to reach the US border. Then they got tear-gassed.

Updated 1317 GMT (2117 HKT) December 18, 2018

Kim Kyung-Hoon/Reuters

Kim Kyung-Hoon has taken countless photos in his 13 days covering a migrant caravan in Mexico. But one image in particular stands out: