Service Brakes Related Problems of the 2009 Mini Cooper

Service Brakes problem

I was driving on the highway 12/04/2014 with cruise control active going about 75 mph. A truck in front of me became too close because he was going slower. My car began accelerating and I hit the brake to slow down, and DE-activate the cruise control. However nothing happened and my Mini-cooper continued to accelerate and I hit the rear end of the truck. I used the cruise control on/off and turned off the cruise control and I stopped accelerating. I changed lanes to pull over, however I had no brakes. I exited the highway as there was a big hill, however with no brakes I went flying through an intersection while honking my horn, and through the red light. The only option was back on the highway after the light and I eventually slowed down and then used the emergency brake to stop. I really panicked and thought I was going to die. The truck had no damage, however the Mini-cooper got a dent on the hood. This also happened briefly about a month ago, where I hit the brake and my Mini continued to accelerate while in cruise control, however when I turned off the cruise control that time, the brakes were fine and I had a close miss of rear ending another car. In hindsight I should have put my 6 speed in neutral or turned off the car. At the time, these options didn't come to me in a panicked state.