Let me see if I understand this correctly.
A border patrol agent fired three shots at kids while standing on our side of the border across to their side of the border, killing one of the rock throwers. Because the kids feet were on Mexican soil we aren't responsible for any liability in his death? I can understand not extraditing him for a crime, but we also can't be sued for this? If the roles were completely opposite would we argue for the same decision?
Since the crime (if you wish to say it was a crime) happened in Mexico then the Mecicin courts is the place for the legal action to be brought forth, not the US courts.