A lot of dogs are not brave enough to confront people who are facing them. When the person moves away, they feel brave enough to move forward. Add to that the behavior is self-rewarding (when I bark and chase, they go away!) I would try having the person turn and neutrally (no hard staring, no interaction) stand facing the dog when he does this behavior. If you have guests and it's not a good opportunity for training, have him on leash or put him away so he can't rehearse the behavior.My 4yr old rescue shin tzu that we've had for just over a year is timid and very insecure. He has come a long way in the year since we adopted him. But he still has issues with people he doesn't know, and most especially when they leave the room. He can accept them walking in, but when they go to leave he barks and chases after them. I have to be ready and hold his collar! He does not do this with me, my husband(but he used to with him) and my youngest daughter with whom he has gotten very attached to like he is with me. But he does do it to my other daughter , who he doesn't know all that well, but he does know her. Plus any other visitors we might have in the house. How do I handle this? And what cold possibly be the cause of it.?