EL PASO, Texas - Border Patrol Agent Ignacio Ramos could hear his heart racing. He could feel the dry, hot dust burning against his skin as he chased a drug trafficker trying to flee back into Mexico. Ramos' fellow agent, Jose Alonso Compean, was lying on the ground behind him, banged up and bloody from a scuffle with the much-bigger smuggler moments earlier. Suddenly the smuggler turned toward the pursuing Ramos, gun in hand. Ramos, his own weapon already drawn, shot at him, though the man was able to flee into the brush and escape the agents. Now, nearly 18...