My cat apparently died in his sleep during the past weekend we are not sure why. He was eating, drinking, using the litterbox normally and he also was interactive/playing normally. He did have a growing black spot in his eye during the past year which didn't concern the vet at his last checkup. The vet believes it was probably some underlying heart condition, but the black spot in the eye remains suspicious to me. I also had a feeling it could be some depression from being in the basement during the weekend by himself, perhaps too much trauma for him? Any thoughts?