Could be a number of reasons, remember all those shares do not have to come from the exact same place. Market makers bundle orders together.
That being said, could be shorts covering, people selling on the news to move on, a flipper who got in low. I don't have enough info on the trade to know for sure.
I love that there was a strong buy at that amount, I wish the price was higher lol but I'm sure the buyer doesn't.