I came to a stop at the stop sign and dropped off the my kids for PE at a local church. After the stop sign I went left going slowly because of kids in the area. I then went around a dark grey minivan that was pulled over on my right side of the road letting her kids out for PE. I then proceeded to take another left. I was pulling into the first parking space close to the PE field, with a fully turned steering wheel, as in doing a U turn. Since I was going slow my right foot was lightly pressing the brake. My minivan was in the parking spot and I was creeping closer to the concrete parking stop with my right foot pressing more down on the brake so I can come to a complete stop. I was about to place the car in park when the engine revved, the car jerked, it accelerated sending me up and over the curb and into the grassy median in front of the parking space and into a tree. The coaches and one other person came running to assist me since I was in shock. There was smoke coming out of the engine so I placed the minivan in park and shut the engine off. The airbags did not deploy.