Im sorry to hear this. I suspect he would go anyway, sooner or later. It become sooner. His only shade of a narrow chance was immediate visit to a good vet and probably followed by massive antibiotica. And that wasnt possible. I suspect it was some form of pneumonia after all.
The non functioning heating pad was probably NOT the cause. It just shortened a little the dying process... Unless its really chilly at your place.
And truth to be said - death because of low temp is less difficult than death by suffocation...
Its sad, yes, but dont accuse yourself. You did what you could, and his soul has no quarrel with you.
RIP, Hulk.
