Brakes Failed problems of the 2011 Toyota Highlander

I was driving my brand new (3 weeks after I bought it) Toyota Highlander v6 in a secondary down hill road when the brake system failed completely and the car started to accelerate downhill. Not being able to control it I ignored the "full stop" sign at the end of the secondary road and I continued in a flat main road where cars normally speed until I was able to put the shift into park and finally the car stopped with a lurch. The life of my son and mine were seriously endangered. The car was towed by the dealer and it is still there after they have replaced at least 2 parts so far. We paid almost $32 000 for a brand new defect free car but insetad they are going to give us the same car which is now undergoing major repairs.