Thanks, Violet, Sabby, and Bebop!
At the very moment I was putting the boxer in my back yard, a man was driving around looking for his female black Lab, which he said had escaped, and was in heat. The boxer boy was not neutered, and he was frantic! Glad I was able to retain him in my yard till the owners came.
Thanks again for the responses!
Oh, and I'll lock my doors from now on!
Love
Patty