I just got 2007 BMW 550i! Love the car but want to know other owners experience..

I know..I had a little scare today..I was in grocery park and just parked my car, then I saw this car that was leaving earlier and turned around and very slowly passing behind my car while I was still in the car. I had to wait until the car is gone before I came out from the car. That car practically almost stop behind my car and I was really scare. Thank God the car gone when I turned my head again. Ugh..it was raining too. I feel safe inside the car but this kind of situation always freak me out lol.