usually this type of trade at the end of the day would be a position assembled by an MM for a big buyer, or distributed during the day for a big seller.
Two days ago a big amount of volume hit on the buy side right at the end of the day--perhaps that was the accumulation and this was the distribution of the position at about the average price (plus a little commission)? If so, then 1% of the o/s just got socked away by a large buyer.