You can't really know. It isn't a big buy in the first place, nor is it possible from what I know. It's spread out across multiple buy orders, and for that amount, it'd be quite an enormous amount of orders. You can try checking for his wallet but I hardly doubt you'd get his info in the first place, not to mention that who knows, it may have been spread across multiple wallets instead of only one. Big trades are made in small portions so that they aren't noticeable in the first place, and so that they don't negatively affect the market.