What if...
...one of my greyhounds passed away at 0315 this morning?

I think he had a stroke.
Was making his way from the bedroom to the den and heard him fall.
I carried him to a bed in the den.
He seemed normal, but wouldn't move any of his limbs.
As I was petting him, he raised his head a few times then sighed and stopped breathing.
He was a good dog - we referred to him as the "Irish Setter of Greyhounds" - he wasn't the sharpest dog that ever lived.
His name was Harley.