http://www.keytlaw.com/arizonawills/gun-trusts/nfa-firearms-in-an-estate/
If at all possible *move* them B4 the owner passes ...otherwise the ATF gets involved...and we all know what that means.
Fortunatly, the deceased had clued in the sole survivor and the executor (fortunately a good friend and not a hired gun) beforehand and the "property" was not declared in the estate, nor was it found when the estate was ditributed. Had there been no suvivor or heir it would have been VERY tricky.
As it was, I had no clue what actually happened to it. It might be at the bottom of a flooded mineshaft someplace. Which is a pity.