At some point empirical reality suggests that the threat to police and others in the US is not from "suspected illegal immigrants," with one alleged Arizona case pointed to over and over for the past several months. Rather, an actual and often expressed threat comes from right wing American kooks arming themselves in the name of fantasies concocted in their own conspiratorial minds and really truly murdering police and others (as Homeland Security warned in this document from last year .pdf).
Yet another case. And so on. And so forth. Etc.