First I've heard of that. But I looked it up, and it's real. HB 2842.

Of course, this is in a backdrop of pretty liberal gun laws. If someone is breaking into your home, you can shoot them. Doesn't matter if they are armed or not. As long as you can show they were breaking into your home, it's open season. It also used to be the case (though I don't know if it is still the case) that if you see someone with your TV in the street, you could shoot them. But...you better damn-well be able to prove it was your TV, or you're in a world of excrement. That law may or may not have changed in the past 30+ years.

azcentral.com - Arizona bill rancher kill trespassing border crossers

It's not specifically aimed at migrants in its wording, but clearly it is in its intent. A rancher (if the bill becomes law) could shoot me (a very white guy) if I was trespassing on his land. Though he likely wouldn't.

The bill proposes a dramatic expansion of the state’s “Castle Doctrine” law, which allows you to use deadly force against someone who is breaking into your home.

HB 2842 would expand the permissible killing zone to anyone who sets foot on your land. All you’d have to do is say you were protecting yourself or someone else.