I think it was a raccoon. I went outside to smoke 10 minutes ago and the cute little black alley cat came over to say hello and get some skritches and then all of a sudden her hackles raised and she growled and got into stalker stance and skulked off toward something she was staring at in the alley. More than likely it was a raccoon, as she's really the only current alley cat. She came back about 3 minutes later and sat with me again and I gave her some treats.