We just rescued a male 50 lb. mixbreed (lab, pointer, and we think pit). He loves people but is wary of other dogs. He gets along with those that he knows, but playing is always up in the air with ending terribly by him not liking another dog being too up in his business. I take him to work, where we have two other dogs that he gets along with very well (no playing!!). However, our office is ground floor downtown so he watches all of the people and cars go by.. and other dogs too. He gets very aggressive at dogs passing by. He'll bark, lunge, go nuts until the other dog passes by. It's scary. I've also noticed this behavior initiates when the other dog makes eye contact with him. I've been on his case constantly to not let him go near the door but that doesn't last very long. He keeps going back and it's very distracting to have to keep getting up. It's gotten to the point where I just keep his leash on and wrapped around my leg so he can't go to the door. What can I do to stop this behavior? I'd hate to have to leave him at home.