This was a FORM T trade which means you do not see the volume from it until after close. Basically the order comes in and the market makers want to fill it but dont want the price to drastically move at one time so they fill the order with there reserve of shares which wont show up as volume at all or fill it in increments on the open market and then print the average after the close.
Everything I say is my opinion only and is not a recommendation of any sort. Always do your own Due Diligence!