Once you start advancing to investigate and to retrieve your dog you notice a man with a knife . You yell for him to stop and drop the knife . If he does anything other than comply or flee , you could make a great case for shooting in self defense . A man with a knife ignored your demands to disengage and instead continued to advance on you and thus you feared for your life and if he got past you , the lives of your family would be in imminent danger . You didn ' t shoot to defend your dog . That ' s not going to hold up , at least in a state like Maryland . However , if you can show that you happened across a violent criminal and tried to resolve the conflict ordering them to drop the weaponleave the property and that they then placed you in immediate danger advancing on you with a knife you should be able to argue the individual had motive , means and opportunity and deadly force was justified . Its you that your defending in that situation . Not the dog .