Big D Hurts

Hey, new guy here. I'm the unfortunate owner of a new/used rx300 and had it go haywire on me on the return part of a vacation. When I got off the freeway after about an hour and a half of driving around 80mph and braked the vehicle began lunging forward and I had to stand with both feet on the brakes to stop it nearly hitting the car in front of me, no warning lights came on, and when I finally found somewhere to pull over and got it in park the engine began to rev up really high (foot not on gas), turned it off obviously, but it still does that when I start it up. Any ideas what might be causing this?