As I said there have been recordings of animals, birds, ice and other objects falling down out of the sky in various parts of the world down through history, the usual BS explanation is a thunder storm picked them up or a water spout or a tornado, usually without any proof that said tornado, water spout, or storm existed.
Since this has been going on for hundreds of years it hardly signifies the end of the world.
Supposedly, according to the "official story", it was dark, and it was not the parking lot that looked like water, but the upper surface of the fog or low clouds above it that were lit from below by the parking lot's lights.
The grebes supposedly "landed", feet forward, tail down, wings flared or folded, on the cloud's surface, and understandably fell instead of floating.
"Just by chance", the cloud's surface was low enough that they couldn't pull out of the fall, and fly; but high enough that most were killed or critically injured by the impact; many were less critically injured or just stunned, and rescued.