Thank you for your question. Here is the answer from one of our vets:
I am sorry to hear of the loss of your older dog and the recent problems you have been having with this dog.
Generally, if there is any hint of aggression, it is time to talk to a veterinarian who specializes in behavior or a certified animal behaviorist. These are complex situations, and it will work best if the professional working with you can actually see what your dog is doing. The dog’s body language is so important. If possible, videotape the dog’s response to people and show it to the professional. The professional will review the video, take a very detailed history and also interact with your dog.
I would not recommend a bark control collar. I would recommend working on general obedience commands like sit and down. I would also have your dog examined by a veterinarian to look for any medical causes for this change in behavior, specifically any painful conditions such as arthritis, or any evidence of cognitive dysfunction. In the mean time, I would suggest an alternative to taking your dog to work with you.
Good luck with your dog!