Last night a friend called sobbing. His companion of seven years, a small, spayed tiger-striped cat, was in his lap, dead. She had been in the house all day, started coughing and having breathing difficulty last night. He was trying to find an emergency vet when she died in his arms.
Because he lives in a semi-rural area, and has noticed her bringing rodents home and eating them,
I thought perhaps it might be second hand poisoning. Here's an excellent article on second hand poisoning from an interesting website you might find useful. It's www.animalpeoplenews.org.
We can't have eyes in back of our heads when we let our animals out - not even in our own yards.
The best thing for every cat is to keep them home and in the confines of the house, without fail.
The link above is relevant to first aid in poisoning. Good to have on hand.