After temporarily building a long position in the E-mini market, HFTs themselves began aggressively selling E-mini contracts in order to reduce their exposure. As a result of the combined selling pressure from the selling algorithm and HFTs, the price of the E-mini contract began to rapidly decline. As other traders withdrew from the market, HFTs began rapidly buying and selling contracts from one another in an effort to control their inventory levels, generating a sharp increase in volume. The selling algorithm responded to this spike in volume by increasing the rate at which it fed new orders to the market, thus exacerbating the precipitous decline in prices.