My prediction is that hopefully an official investigation of the case is started, evidence is gathered, and a jury gets to deliberate on the available evidence whether the fully armed and trained government officer acted rightfully or wrongfully by shooting and killing a 15-year old, or even establishing whether the former was even throwing a rock at all [despite many claiming it here as fact, most eyewitnesses claimed this was not the case] - seeing as the very Border Patrol did not so much as initial any investigation, as they themselves have acknowledged it.
I'm my humble opinion I'm opposed in principle to any armed government officer opening fire on a 15 year old lest in some pretty extreme circumstances of pressing danger, whether it be Tunisian or Israeli or Chinese ones or this Border Guard - this happened across a river and international border, and from behind a high, reinforced border fence. But hey, who knows? In theory the Jury should know better than I, after looking at all the facts.