why did the border patrol shoot jose antonio elena rodriguez? and why are questions involving his death met with silence? tonight, fault lines examines the nations largest law enforcement agency and asks who is holding them accountable when they pull the trigger. >> people here call this ambos nogales, or both nogales. but a steel fence built in the name of national security divides this border town. i've come to meet jose's family they live just blocks from where jose was killed. >> his brother diego worked at a shop in the center of town. jose would often meet him to help mop the floor before closing. that night, he never made it. jose antonio was shot to death, right on this street corner. the walls on this doctors office are still riddled with bullet holes. now, the border patrol's explanation for what happened hinges on the fact they say their agents were threatened by somebody throwing rocks on this side of the fence. but standing here, the first thing you ask yourself is: could a 16 year old boy really threaten somebody standing on top of

. >> jose antonio elena rodriguez was 16 when he was killed with a bullet through the head by the united states border patrol. nine more shots went into body, as he lay on the ground in his hometown, nogales mexico. the bullets fired from the top of this cliff in arizona traveled through an international boundary, and into a legal vacuum. the agent has never been named.