Sudden dealth cat

Question
Thank you for your time in responding.  We just lost our 7 yr old male cat suddenly this morning.  He is mostly an outdoor cat that would come in for occasional naps.  He was laying outside on our garage floor unable to walk.  I picked him up to move him and he let out a groan and meow and poop started coming out of his behind.  I had called a few vets and they said to bring him in but within the 1/2 hr he had died.  The only symptom he had shown was some mild limping the day before and the occasional vomiting usually accompanied buy a hair ball.  He did throw up yesterday as well that only had cat food in it.  He killed and ate a lot of mice.  Regretfully we were behind on his immunizations.

My biggest concern is we have three small children one being under 1 and if he had something contagious that could be passed onto them.  My 10 month old had a single pin worm about 3 weeks ago that I assume she got from the cat, that has been the only one so it seemed to be isolated.  I didn't know if that info would matter.  The only other thing I noticed (since his death# that he was using a box of lyme#plant food for grass)for a litter box.  We had it in a bag that got wet and tore so we put it in a box in the garage.  Could that have poisoned him?  Thanks again for your time.

Answer
First I want to say that I am sorry to hear about your cat. It is never easy to lose a pet. It is hard for me to know what could have done this to your cat, but there are many things that outdoor cats are exposed to.

He could have been hit by a car. He could have eaten a mouse that had been poisoned. That can take days to kill the cat but it will eventually make them bleed to death inside.
I don't know what you mean by Lyme plant food, but unless he ate it, I don't know if it would have hurt him. If it had lime in it, that would have burned his feet and he wouldn't have used it.

Snail bait is poisonous but cats don't eat that kind of thing. He could have gotten into some antifreeze however and it only takes two licks to kill a cat within 2 days of kidney failure.

You could take him in for a necropsy if you are concerned about contagions, however, it would be hard to say what those could be at this point.