Quote Originally Posted by Killer Kitten
Hopefully things have settled down and gone back to normal in your apartment.
It could be that your cat was trying to tell you something about that stray cat outside your apartment. Something that he could sense but that you could not. Perhaps the cat is FeLV or FIV positive, or even sick with FIP.

It is always a good idea to keep your cats indoors and not let them associate with unvaccinated, untested stray cats. Your cats will live longer, healthier lives and you'll save a ton on vet bills.

You'll also avoid issues like this one.
Shadow is still hissing at the youngest cat, Stormy, but he's settling down.

Him & the stray have sniffed at each other in the past. But the stray has recently had a litter of kittens (whom I have already found homes for all, including Momma cat) and I think that was the problem. The *ONLY* time Shadow goes outside is under my close supervision. He's never unattended out there. He enjoys being outside and since he never runs off, I don't have a problem with him being outside with me there.

Momma has also been vaccinated & tested, once I found out she was pregnant. My vet agreed that because it is very difficult to find a home for a pregnant female, to let her have the kittens, then adopt them all out. She will also be being spayed before she goes to her new home next month. Momma has no diseases, which is the other reason I don't have a problem letting Shadow outside with me.

Contrary to what you seem to believe, I am not an irresponsible companion to my cats. All 5 of mine are vaccinated, spayed and in perfect health.