Loss of another Dad

I lost my father-in-law tonight. He passed away at 5:45pm from a sudden cardiac arrest. My husband and I are still in shock, I think. This man was, other than having diabetes, in great health.

He'd just come in from walking his dog, sat on the couch, happy and talking with my mother-in-law when all of a sudden he took a deep breath, threw his head back and slumped forward. That was it. He was dead.

It's such a shock to lose him so suddenly with no warning. I don't quite know what to do.