I am thinking that someone bought 4,000,000 shares by exercising 40,000 calls. It wouldn't make sense to exercise the puts since the market price (120.34) was higher than the strike price ($120) at the time.
Let's assume that GILD did sell the puts and buy the calls...wouldn't it be fantastic if the stock closed at 119.99?
GILD would buy 4 million shares from the puts. And, if I were the company, I would exercise those 120 calls as well even though the price is lower than the strike price, since buying it through exercising the options is price and time independent whereas buying it on the open market would undoubtedly drive the price up and would take a few trading days to do.