2007 CHEVROLET AVEO User Comment / Complaint

I had stated my 2007 chevy aveo, pulled the parking brake very tight. when i returned the car had rolled down the drive and into a neighbors tree. my first thought was, duh, i didn't pull the brake. i got in the car, and the brake was not only pulled, but was only 1 click away from being fully engaged. the driveway my car was on, was no more than a 10-15 degree angel, the car was not loaded with a lot of excess weight. again the parking brake was fully engaged. why in the world did this simple part fail? it seems to work now, but that second it failed. my car was only damaged it is only a matter of time before someone is killed from a rolling aveo that was in park. thank you for your time.