[Dave W]

I would guess vandalism. These frameless windows pretty much float with the rubber seal around the outside acting as shock absorber. Settling probably wont cause a problem but major temperature changes in a short time might - but this is tempered glass much like the windows (except the windshield) an you vehicles which seldom mysteriously break and dang strong unless a rock or hammer whack it and pretty hard. Of course with a San Antonio hail storm. anything could happen as one of our daughters found out a couple years back.

Hope your insurance folks are good for it - these are not inexpensive to replace even as a DIYer.