After Darfur's el-Fasher falls to militia fighters, revenge killings begin

Atrocities continue as Sudan's military retreats from el-Fasher, a town in Darfur that has been under a grueling siege for more than 500 days. Nathaniel Raymond, the director of the Humanitarian Research Lab at the Yale School of Public Health, tells The World's Host Carolyn Beeler how high-resolution satellite imagery is documenting crimes committed by the militia known as the Rapid Support Forces.