It was a forced trade to satisfy an obligation To fill an order imposed on a participant or access person by any provision of UMIR or a policy and that is entered on a protected marketplace to execute as against the disclosed volume on that marketplace prior to the execution or cancellation of the balance of the order - taken from iiroc rulebook. Basically they were trying to pull the order but couldn't and had to sell?? I'm a newbie but it's my best guess