i can't process this death

I don't even know where to start. 

This has never happened to me.

I got a call from a client this afternoon, and it was the worst news ever.

I saw her two cats yesterday and for the two days prior. 

"Kristen, it's Ann*. We just got home a bit ago. When we got home, we found Princess dead."

Ann was kind as can be. Not accusatory in any way. Perfectly respectful. I'd left her a note yesterday talking about how great the cats were...how much love they got. Princess was affectionate, as always. I saw her eat and drink and use the litter box. I left her purring on Sunday. I've taken care of her several times...I know her well.

Ann just simply wondered if I'd noticed anything different about Princess. I told her that I would, of course, have called her had I noticed anything amiss. She said she knew I would have, but just had to double-check. I was crying. I didn't understand.

I don't understand.

I just saw this cat less than 24 hours ago, and she was perfectly fine. Now she's...dead? This doesn't make sense. I can't process this.

I loved this cat. I left her fine. And her parents come home to find her suddenly dead?

I wish I had better words. I don't know what to do or how to be right now.

*Names have been changed in the interest of privacy for my clients.