That is Not My Dog

What is the etiquette when someone else’s pet follows you on a walk? Yesterday I went for a walk after dinner and this big yellow lab found me and decided to tag along. I never saw him before and don’t know where he came from. He was the kind of dog who runs up to other dogs and barks, and runs into people’s flower beds and runs in front of cars — not the kind of dog I want to be associated with. I tried to ignore him. I tried to shoo him off and send him home. Meanwhile, people are saying things to me about “my dog.” I just kept walking. I didn’t feel like it was my duty to figure out where this dog belonged and take him home