Some extract from ITG ...They are the ones that bought at the end...This is part of their published strategy
Trading Strategy Implications: Rebalance Trades vs. Flow Trades
Institutional trades done around the close typically fall into two categories: rebalance trades and flow trades. Rebalance trades are those where a portfolio manager is using existing positions to finance a trade. Flow trades, on the other hand, are those where the trade is being done to invest inflows of cash from investors or to generate cash to fund a redemption. An investor redeeming mutual fund shares, for example, would receive the closing price on the date of the redemption, as opposed to at the actual price received when the fund sold shares to raise cash.