Has anyone unrelated to the drug or trafficking trades ever been caught murdering illegals?
In the general sense, I am sure of it. Illegals get into America and are subject, more or less, to the American environment which includes murderers.
In the sense of "murdered at the border while invading to stop the invading" I have not heard of it. If it had happened, you can be sure it would be played up early & often. Maybe oftener than the poor Sikh who was murdered shortly after 9-11 is dug up and paraded around.