Before this will be considered a clean deal that mysterious buyer must be identified.
As far as I know it's not illegal to buy and sell stock in public companies in the United States of America and there are no laws that require the disclosure of all buyers and sellers of same. The real question is, as discussed in this article, did then-private citizen GW Bush use insider information to sell stock that harmed the buyer and avoided a loss for the seller. Since the stock rebounded to its pre-sale price the next trading day and doubled within 12 months of the transaction, it seems to me there ain't no reason to worry about who the buyer is unless one is interested solely in "the politics of personal destruction".
According to an interview with Bush's broker earlier this week, an insitutition approached him about buying a block of Harkern.
He went to several of the board members before approaching Bush. Bush told him he first had to determine whether the transaction was legal. Sorry I don't have the time to find a link for you, am getting ready for Church.
Do a search under "Bush broker", and you'll probably find a couple or three threads that ran earlier in the week.