Oh, wonderful. Apparently not content to address the problem at its actual source, which would be cheaper and more effective, you instead to propose a shoot-to-kill policy that would never be enacted in any case.
Ammunition isn't expensive, and Mexico can pay for the funerals. Plus, it would only take a handful of carcasses to discourage the rest.
Given that the wussies in Washington wouldn't accept my logical, workable solution, what would you recommend to stop the influx of illegals and persuade the ones that are here to go home?