Why this? Why now?

My family life is spinning out of control and so is my relationship. My mother's boyfriend is kind of an ass and my boyfriend hates him so much for a lot of valid reasons. Last night my mom's boyfriend threw his shoes at my kitten for no reason at all and now my boyfriend said the peace between him and my mom's bf is gone. My boyfriend is getting increasingly aggressive and it's scaring me he used to be so sweet and lovable and now I hate to talk to him because he just gets angry and it scares me and makes me upset. I don't know what to do I feel as though he just doesn't care about me or anything for that matter. he's willing to destroy me and destroy what we have over his anger and hatred. What kind of person does that to someone they "love". Why is this happening like this? Why doesn't he care if he's hurting me and others? Why won't anyone listen and help me for fuck's sake? I just don't get it...