Someone keeps dropping 100000 lines on the sell side regardless...

Someone keeps dropping 100000 lines on the sell side regardless of bid price. Someone wants to lighten after recent run and before news or wants out altogether. Holding the price down by undercutting the offer and taking out the big bids at every opportunity. Can't be CBA this time so who is it that can do this day in day out pre announcement? Hope they are just locking in some profits, lowering exposure and diversifying elsewhere.