!!heellpp!!vy sv8 commodore bad noise in rear!!

[Coxy92]

Hey guys need some major help!! Whenever i put my foot on the brake to stop pretty well as im at a full stop i hear a sliding type noise then a bang happens it switches from the Left to right hand rear side of the car every now and then and nothing in the boot is doing its spotless in their. Any idea what it could be?? Please HELP!

[Coxy92]

I also just recently bought it of a dealer and it just had a service and a 104 Point RAA inspection. But sounds like its near the Brakes,Rotor area????