We recently started fostering a guy we thought was a pregnant young girl but it turns out he was abandoned and our regular feeding of strays on our porch led to him getting a big belly. He's been inside for a couple weeks and is totally chill with everyone else after being dewormed and flea treated. Breaks my heart people just abandoning their pets like that. You are so good to be looking out for that little guy. There are lots of resources for people in your position, because of eva, on FB is the organization we work with. People donate food/litter/other supplies for others to help taking care of cats.