That's really sad Jon. It was very cold here in Norfolk last night wasn't it?
I remember when 'Solo' appeared in the snow in the huge garden of our last house. He too was gazing wistfully at the lighted windows, lifting up one paw after the other as his feet were slowly freezing.

He fled when I appeared bearing a plate of food for him. But crept up to eat it once I went indoors.
I actually cried, it was so pitiful.

Little by little he got used to seeing me. I took to taking a mat onto the patio and sitting there on the ground, with the dish of grub not too far from me. (I hate the cold and it nearly killed me, but still...)
He gradually ate his food warily with me beside him, but I didn't move or try to touch him, just gently spoke a few words each time.
This went on for days.

Then I moved the dish nearer to the back door. Eventually, he peered in and saw the other cats stretched out sleeping in the warmth, and poked his nose in for a split second.

Finally, he decided to risk it and came indoors. I left the door ajar (waste of heat, but there it is) and he plastered himself against a radiator and fell asleep.
The other cats were strangely accepting of him. I think they sensed his suffering.
He absolutely adored us after that, and would sit literally wrapped around my neck while I watched TV.
We had to work on his matted fur, fleas, worms and general ill health.
After two years though, his belly swelled alarmingly and the vet told me he had advanced liver disease and advised euthanasia.
I sobbed, but one has to do what's best.
At least he'd had two years of love and luxury.
My husband was terribly upset as well, but agreed we'd done the right thing.