I think it's worse when they die suddenly like that without any previous warning or signs. One of my "soul" cats died of a heart attack at 15-1/2.....fine when I went out and when I returned, she was not at the door to greet me as she usually was. Didn't see it coming at all and the shock is worse than other cats I've had die of old age and declining health. My heartfelt sympathies to you. I truly believe that some day we'll see our beloved pets again.
"No heaven will not ever Heaven be; unless my cats are there to welcome me." ~ Unknown
Sorry for your loss,
from one who recently lost a companion of 16 yrs, I know how you feel...in our case we watched the end come, although relatively no severe pain, he still was not himself. He and we endured and finally he passed on...
While the loss is great no matter how it happens, we must accept it.
My heart goes out to you. I know that hurt, shock, and devastation when they suddenly pass without any indication anything was wrong.
I too would love to hear more about Tuffy.
Sounds like he left with a piece of your heart.