Sorry mate, bad luck.
But don't feel disappointed neither pissed, for when something reaches the end it is just because another time begins, new doors are opened... Maybe this is time to start with a small pygo shoal, why don't you try some little caribas? it is true piranha season is about to start.
If you kept your fish for 4 years and then he died I wouldn't see this as a failure, you kept it doing quite well after all.
Chin up bro!.
Cheers.