Sudden death of cat

[tripseven]

Good Morning,

I realize that this will be a difficult question to answer and I will try to be as specific as possible. We had to go out of town for a family reunion. I checked to make sure the cat was not locked in a room etc. He was on our bed and seemed okay. There was some vomit on the family room floor but this was not so unusual as sometimes he would gorge himself. My step daughter came home from college the following day and the dog and cat were playing in the living room and all seemed well. We returned home this past Sunday. I went down stairs to put the luggage away and found our beloved cat dead on the laundry room floor. I found a pool of what I believe was bile(very dark green clear liquid) next to the litter box. The cat appear to have just laid down and died. His eyes and his mouth were closed. There was a light greenish liquid trail from his mouth to the floor drain. It appeared that he was eating his food but there was very little urine or feces in the litter box. There did not seem to be any sign that he thrashed or struggled. Based on the state of rigor he was in, I believe he must have passed sometime early in the morning. Jazz was twelve years old and showed no signs whatsoever of any illness. My concern is that perhaps he got into something poisonous but I cannot imagine what that would be and I do not want our dog to suffer the same fate. Any light that you can shed will help us to better deal with his death.

Thanks so much in advance.
Bill