Very sorry to see this, I hope the vandal experiences a painful death. For what it's worth, those parallel marks look like they were left by a fork, rather than a key. Of little value I'm sure but perhaps that might help with your investigation.
2011.5 LeMans Blue e92 DCT, ZCP, European Delivery. Edition Grilles, Reflector delete, Rear Fogs Enabled, Encore Innovation Exhaust, LUX Angel Eyes, 255x285's, Dinan 3.45 Rear. "Last of the V-8 Interceptors, a real piece of history..."