Looking at the pictures whatever hit your 5er suffered a broken rear hatch window or rear door window. Probably someone with an SUV. One thing for sure, they knew they did it.
I'd definitely find a new lot with cameras at the very least at the entrance/exit. If there were cameras it would be pretty easy to see a blown out window on a vehicle.
The positive side is it appears to be only cosmetic and a gel coat repair is in order. Tape it up for now so moisture doesn't get in.
*Current: 2005 Ford F350 Crew Cab Dually 6.0 diesel 4x4*
*Retired: 1987 F350 Crew Cab Dually 6.9 turbo diesel
2007 Forest River WildCat 32QBBS