Problems with 2000 Buick Park Avenue VEHICLE SPEED CONTROL

I was driving a buick park ave 2000. after stopping at a stop sign i made a right hand turn onto a busy 3 lane city street. when i accelerated and began changing lanes the car lunged a little and continued to accelerate on its own. i tried pressing the brake and it felt like there was a block of wood underneath it. the brake was not working and the car kept accelerating i was approaching a busy intersection and the light was red. i tried down shifting but nothing changed. i kept trying to brake but .it didn't work and the car kept accelerating so as i approached the red light the only thing i could think to do was try making a sharp turn with the cars that were turning headed in the opposite direction i was going. i managed to slice between two cars in the turn but the steering wheel became incredibly stiff and i couldn't negotiate the turn as hoped. i ran into two cars that in turn were pushed into two other cars as a result of my not being able to break or control the steering into the turn. there were two people who went to the hospital and had injuries. *tr