I don't think they just bought them. I think this is a form that the "beneficial owners" (> 5%) have to file every year within 45 days of the calendar year end bla-bla. If you look back through that same set of filings, you'll see pretty much the same form every year at about this time. I believe those people have owned that stock pretty much all along.
(If you're feeling masochistic, here's a link to a pile of legalese, which is the reason those SEC statements were filed.)