So very sorry to hear of your loss, Judith. Casper sounds like a wonderful feline friend. I lost my dearest cat, Buddy, two years ago now, and he was by my side for 20 years. But like you, I can still see his shadow in my home, and I swear I can still hear his purrs.
The tears are rolling down my cheeks right now, because it was only four short months, the identical thing happened to my beloved cat. He was such a good brother too. Nothing is worse than having to put an animal down, but even worse to see them suffer. Heartbreaking write.