OK, thanks for the info. From the symptoms you described, it sounds like there was DIC, which is short for Disseminated Intravascular Coagulopathy, which is a condition where the blood clotting factors are used up by the body, sometimes because of severe inflammation or other illness. Once the blood cannot clot, then there is usually bleeding
noticed from multiple locations as you described. The fact that the back legs were unable to move, were cold, and had no pulse, suggests that there may have been a clot that formed in the arteries leading to the back legs, or that the output of the heart was so poor that no blood was reaching the hind end.
The presence of the high fever suggests that Heat Exhaustion may be to blame, which is an awful disease because the prognosis is so poor. It commonly results during the summer when dogs are left outside or left locked in a car, for example, but can occur under other conditions, especially if they have any breathing problems that reduce the ability to get rid of excess heat.