So sorry to hear this,
chuggie. It's hard enough when you know it's coming, but so out of the blue like this must be twice as rough.
Even though Sam was sick for years and every day we were given with him was a gift, it still wasn't any easier when his time finally came.
Cry and cry some more. When you think you can't cry any more, cry again. It helps. What was the most therapeutic thing for DH and I was doing his memorial page at Rainbow's Bridge. It's in my signature if you have the signature line function turned off. That allowed us to both grieve and celebrate Sam's life at the same time. While I still miss him terribly, I can remember him with a smile now.