BB or a pellet gun. With that sized dent, I'd say it was a pellet gun. BBs, i think, are very small and plastic. Pellets are a type of metal.
Hope you were able to notify the police and let them know where it happened
'06 BMW E46 ///
: '08 BMW E60 DINAN ///
M5, Interlagos Blue, SMG
DINAN Stage 2 Suspension, Exhaust, Stage III Software, Front strut braces,
Intakes, 13% Underdrive pulley, 3.91 Differential, RPI Scoops.