This is what I know about the other cats in the building. My human talked with some other humans about them this afternoon.
So Wednesday, he saw a tabby on the balcony. This cat looked like it had been in a little fight, as you can see by the scratch on his face. There's an orange cat named Bob, and a black cat whose name he missed. All three of them live downstairs with a vet tech who works in the next town.
One of them caught the mouse I heard in the wall last week. I didn't see it, but I stared at the wall from the bedroom side and the kitchen side. I tried to get real close to the wall. I wasn't letting my human sleep, so he got up and did dishes . By the time he was done, the mouse had calmed down.
He's been putting out some food for them and the grey feral, but it was so windy this week that the plastic dish blew off the porch. He found it and brought it back up. (He wasn't using the plastic on Snowy Sunday.)