I'm guessing it was shot at by someone. With what, I don't know. There is a footage shared by Breitbart of the destruction, followed by a car fleeing the scene.

The debris seem to scatter in one direction and I'm not sure if a bomb would still be powerful enough to destroy one slab but not affect the others. Whether it is by lightning or someone, this should send a signal to the DS.

Or maybe, this is a distraction by DS? Maybe there's a time capsule they want to retrieve? Who knows at this point. Gotta consider from all side.