Both of these statements are probably right on the mark.
From the news reports, it doesn't look like the IRS was seizing anything other than possibly their books and other financial documents.
While I have absolutely no love for Gunsmoke because of their shady business practices, I've got to wonder if this investigation started because they were a high profile gun store, or if there was legitimate reason to believe the Gunsmoke owners haven't been claiming all of their income properly, or both.