It's a frigid, dark night in the mountainous border region of southeast Arizona. A group of 31 suspected illegal immigrants are walking up and down rocky ridges toward Tucson, Arizona. They're wearing small backpacks and stop to rest every few minutes.
This isn't a scene unfolding before the eyes of Border Patrol agents on the ground. It comes from a video image provided by a Predator B unmanned aircraft 19,000 feet overhead.