sudden death

Question
I am sorry for the length of this but I want to give as much info as I can. My 10 month old kitten suddenly died last night 5 mins after I got home from work. He was running around like normal, followed me into the bedroom, laid down on his side and it looked like he was kicking with his back paws, but then something didn't seem normal so I went closer to look.  He almost looked like he was having a mild seizure (he never had one before) because there were a few strange sounds (like gasps) and movements coming from him, so I bent over and gently petted him.  I thought (and hoped and prayed) maybe he was having a mild seizure and would snap out of it in a second or 2.  After several seconds it was clear he wasn't responding to me at all, his open eyes seemed "gone" and the truth was after the 2 initial "breath/sighs" he had made, I couldn't see anymore breathing nor could I feel a pulse. There was a little white froth around one side of his mouth but very little. He did not urinate or poop.  I believe what I heard initially to make me stop what I was doing was a little strange breathing. No crying out or frantic movements at all.  I have 3 other cats, one of whom is a 9 month old kitten and was his inseparable partner, and 4 dogs. I looked all over to see if he could have gotten into anything and cannot find a thing. My friend came over and checked him mouth and couldn't find anything in there. He was not the type to look for things to get into or pick up things on the ground, in fact, unlike the other cats, he wasn't a vulture about eating. He was in good health and up to date on all his shots, and strictly indoors, although the cats were allowed on the screened lanai.  Unlike my other cats, though, he might run in and out, but he never hung out there looking for bugs or lizards. About 24 hrs. earlier the cats got their advantage multi-cat topical treatment, but had no prior reaction. My questions are what does it sound like could have happened; does it sound more like a toxin, and if so, could it have been a reaction from the advantage that long after, or something else? Also, if I wanted him looked at by a vet, is it too late?  My vet was not at work today. I am so devastated and miss him so much and don't know what to do. Any assistance would be appreciated.

Answer
I am so very sorry to hear about your loss, I am sure it is devastating. Though medications have been used before there is always a very slim chance of adverse reaction.  Another possible cause of sudden death is undiagnosed heart disease.

The best thing to do if you wish an autopsy done it to keep his body cold until you are able to get him in to your veterinarian.

Again you have my deepest sympathies for your loss.