I have lived with my boyfriend now for almost a year he has a 3.5 yr old German Shepherd x who has becoming increasingly aggressive to my 8 yr old Mountain Feist. For no reason at all, just today she attacked my 26lb dog for no reason. Thank god I was in the yard! She turned on him.. no reason at all and lathched on to his neck (which was basically half of his neck in her mouth). She didnt puncture his skin but if she had.... no doubt she would have killed him. It took about a minute or so of kicking and punching to get her off of him. i dont know what to do. There were no signs.. no change in behavior, no hair raised, she just turned and bit him. I have worked around animals to notice signs and there was nothing. I just dont know what to do... any advice would be great. Im still really upset about but its just not fair to any person or animal in this situation. Sorry, still really upset right now so sorry if its all a bit jumbled.