My car was parked and shut off on a slight incline. After about 3 minutes I saw car going back down hill hitting the car behind it. As I ran to car it was still moving. I jumped in the passenger side because driver side was smack against the other car. Then I climbed over to the driver side to get my foot on the brake. It was still moving the whole time and picking up speed. There was snow on the ground but it was not icy. I do not think the snow had any relevance to it.

I purchased the car in July 2015 and a similar thing happened early on in my ownership but I didn't think to much about it. I got out of my car and still had the door open and noticed it going back so I got in and put on the emergency brake. I never used the emergency brake again. I am concerned this could be a bigger issue but have not found anything else online about it.