According to Ashford he collapsed and died on his way to his paddock.
http://www.paulickreport.com/news/bloodstock/top-young-sire-scat-daddy-dies-at-11/
I just saw this on their FB. 
He was only 11. Such a shame.
No!!! What a huge loss.
Only 11?!? Such a shame. Condolences to his connections.
He was such a nice sire.
Nice sire and such a loss. Ashford must have been in shock when it happened…
RIP Scat Daddy
He was one of the best younger sires. It will put a huge hole in Ashford’s business.
Such a lot of bad news lately…
What a shock. Condolences to his connections.
