There's a bridge at Panau City that causes this when you drive through a certain point. Maybe there's more points like this. Has this happend more than once at the same place, or at a different location each time?
I play on PC, and also it happened again today, I was going to the three kings hotel, and a statue that was below me was destroyed by a clumsy driver, which I assume. So it usually happens when I am boating or parachuting at certain areas, it seems.