One question is why he sold all those shares in one batch. He could get significantly more if he sell them slowly along this week. Even he knows something we don't know, it's still far way from the deadline, 10 Sep. so most likely he may just need cash desperately this time.
If you're a whale you don't care about that sort of thing. Even if you sell slowly you remove buyers from the buy side, and if people see the price dropping they may cancel their buy orders. If you do it all at once, you take everyone by surprise and no one has time to remove their orders. If he broke it up in chunks of 10 each, it would still move the market.
It's likely someone taking profits. My shares are still worth WAY more then I paid for them.
