What's worse then losing a pet

Three weeks ago one of our addopted kitties dissappeared. I just figured that maybe He found a female kittie. He was a local tom cat that addopted us and has been with us for almost a year. Well, I was walking up to the post office today and saw something odd out the corner of my eye. I wish I hadn't, but I walked up closer and found, much to my dismay, the decomposing remains of Bob Kittie. I am so upset and feel so bad that he died alone. I don't know if he got hit by a car or was killed by the coyottes or an owl. It makes little difference now. I feel so awful that I saw this horribly decomposed body. How can I get it out of my head.