No one has been arrested? How do we know he was an illegal?
It's probably an assumption, based on the fact that he was responding to a report of an illegal needing help; that, and probably some good detective work at the scene of the crime.
These are the same things that led LEOs to believe Rob Krentz was murdered by an illegal last year.
FWIW, the Krentz killer has been known to use this same drug corridor.
While I understand your point, you clearly don’t understand the situation in that part of the country. Oh, you’ve heard about it on the news, but that can’t completely relate the reality. The man had good reports that there were illegals in that area, and so he responded. What do you think the odds are that it wasn’t illegals? My money is on a cartel hit.