On two occasions this week, friendly strangers have stopped us on a walk and asked to pet my 2 year old Boston. He sits and lets them while they pet him for a moment, speaking kindly, and then out of nowhere he barks ferociously in their faces! It's startling and embarassing and now I am paranoid when people approach. Nothing is new or different about our routine. Is it because the people were bending down over him and he was threatened? The second time, I hunched down beside and kept a hand on him, but still he did it again. I would love to hear some suggestions please.