BROOKS COUNTY -- It's just before noon in the tangled woods of La Copa Ranch. U.S. Border Patrol Agent Rick Garcia makes his first discovery of the day. Through the web of mesquite brush and weeds, the footsteps of three immigrants crunch louder on the blanket of dead leaves as they approach the weathered ranch path. Garcia's partner, K-9 agent Chico, just found the immigrants struggling through the woods. Garcia asks the exhausted group in Spanish whether any of them have weapons, then how long they have been traveling on foot. "Two days," one woman replied in Spanish. The group...