Our 4 Year Year Old Kitty Died Out of the Blue!!!!

Hello to all.

We have had a terrible family tragedy. Our most beloved cat, Austin, dies
suddenly yesterday for no apparent reason. He had been acting perfectly
normal and loving like he always does. I went to take a nap (as I often do
on Sunday's) and Austin always lays next to me when I do. When I woke up he
was lying next to me, per usual, curled up and head on a pillow. I started
to pet him and my first thought was, boy, you sure are sleeping deeply
(usually all cats will flinch or wake when they are sleeping and you go to
pet them). I then realized his eyes were half open and he wasn't breathing.

I have NEVER seen anything like this. He must have died in his sleep.
There was no vomit, no urine, no signs of distress. He appears to have
instantly died in his sleep. He was only four years old and was our most
favorite cat of our six cats. Needless to say, my family is in a state of
morning today. My wife is worried that whatever killed Ausin could kill the
other cats, but we had just wormed all our cats so we can pretty much rule
out heart-worms.

My sister-in-law suggested a brain-aneurysm. I thought perhaps massive
heart failure.

Does anybody have any thoughts on this? Should I be concerned for my other
cats? Any advice or information would be welcome. Thank you very much.

Nick