I came back home and an unknown cat was inside my house. I have 2 cats already (8 years old female and 6 yr old cat). The female one smelled him for a bit. I called for her to the living room, both came (the female and the unknown cat) and she was pissed and almost hit the little one.
How should I proceed?
Separate the unknown cat, post it on Facebook that you found her, Craigslist, see if any local shelters will put her up on a lost and found, look for lost and found web pages and apps for your area, put up fliers, bring her to get scanned for a chip. If you can't keep her in your home, bring her to a shelter or call ACO and tell them you found a stray. The cat legally becomes yours in most states after 2 weeks of taking care of her.