Doesn't sound like due process was served... I guess that's what happens when nothing is certain, but death and taxes.
Hopefully the family gets something out of this except a punch in the face.
They can now go to court.
In the meantime OTHER Administrative Due Process is moving forward regarding unpaid income estate taxes.
You have to differentiate between "Administrative" and "Judicial" processes. They are different ~ as befits our divided system of government ~ so Treasury did it's trick and the Courts will do their trick, and eventually these people will be beggared or given the coins.
Unless Treasury can make a criminal case here, or fraud, the taxes are no longer payable, so it's possible Treasury has somebody tasked with working up a criminal case. In which case the original taxes (plus some interest and penalties) are still due.
The answer is THEY SHOULD HAVE KEPT THEIR MOUTHS SHUT.