You would have to be pretty determined to cook up false documents and keep the scam going for more than 10 years, as appears to be the case here, in a state (AZ) that isn't particularly friendly to non-citizens (and even citizens, if they're the Wrong Color or Ancestry). If he had a valid AZ license, especially commercial, it suggests strongly that he was legit. Go take your tinfoil immigration hat to another place where it's appreciated more.

I suspect that, once the facts are finally assembled, it will show that he made a bad mistake, turned at the wrong spot, and didn't know or think about the consequences. Yes, those are bad things to do, and in this case resulted in death. It probably was not done intentionally. However, the consequences, including criminal prosecution, in a case like this can be significant even if the guy didn't intend anything and it was really an accident. So, again, we'll see what happens, but at this point he doesn't appear to have run away.