Last Tuesday night, my 4 year old cat was his normal self. He was a healthy cat. The next morning, I found him dead in his bed. He had to have died sometime that night as his body was already stiff. The vet did a necropsy and all they could find that was unusual was that his tongue was slightly thickened/swollen like he bit it. Any ideas on what could have caused his death. The vet didn't mention anything wrong with his heart.