general problems of the 2001 Lexus LS430

I turned around in a parking lot by backing up and reversing my direction, after I reversed my direction the car shot forward without my foot on the gas pedal. I kept pumping the brake hoping it would stop and I shot out of the parking lot into the line of traffic and avoided two lanes of cars driving west until I collided with a car heading east. It ripped off the front bumpers of both cars. I felt trapped in the car and could not control it. It just kept accelerating. I wish that I had the presenceof mind to turn off the key or push the automatic lever to neutral or even reverse. But it all happened in a few seconds and I just didn't have the presence of mind to do anything but step on the brake pedal. Just once before, some months ago, I was parking the car in a public garage and it accelerated quickly asi reached an off ramp. Luckily I was able to turn the steering wheel and negotiate the car around the corner onto the ramp. It scared me, but I thought it was just a freak incident and thought no more about it because I was able to slow the car down once I went round the corner. But this latest time I couldn't stop it and the car is a total wreck.