That ESC is designed for for NIMH cells and doesn't have low voltage cutoff for LiPo Cells.
Input Voltage Range: 4-8 Cells (4.8 to 9.6 Volts DC)

So you are running a battery that is higher voltage than it can handle. You probably shorted out all of the forward MOSFETs and are having to use the reverse MOSFETs to short the battery to get it to stop. Do not use that ESC ever again or you may burn your car down when the battery catches fire.