Windshield theories

I currently have 3 theories on the breaking of esmerel's rear windshield.

Upon inspection, there is pretty clearly breakage point, and it's chipped on the outside. So something impacted it.

My theories are:

1. Errant Projectile (i.e, baseball or bullet) but it was retrieved because I find no trace of such a thing.
   
2. Damn Kids (but they usually don't stop with just one whack)
   
3. Stupid Garbagemen (because it *was* garbageday and the garbage cans are right by the car.
   

Theories narrowed:

I found a marble on the other side of the car. That narrowed my theories down to "Damn Kids."