Otterpop

Ive only had this happen at really low speeds but about 8 or 9 times when I have been slowing down and turning, such as around a corner, changing streets and in parking lots - the brake pedal kicks back and releases itself while making a loud hard clunk. I bought the car in January. The dealership says they had just replaced the brake pads. This first occurred in April, of course after the 3 month warranty expired. Im hoping this is something small. Please please let it be something small.