What do I do about my abusive father towards my two dogs?

My dad has abused both my dogs. One is a miniature Maltese, who is very old and used to have seizures every night when he was young, and the other is a Red Healer mix, just a little puppy. My dad is aggressive towards my dogs when they pee and poop on the carpet and he throws objects at them. Just today he left the screen door open to allow the Maltese to run out and my mom saw and told him to go get him and my dad grabs him by the back skin. Does this hurt the dog? I know how it doesn't hurt cats because they have extra skin on their necks but he seemed like he was in pain. I warned my mom about his abuse but she didn't think much of it and I need my sister to come home to tell him off because I'm not getting rid of these dogs because I love them. What else should i do? I'm not afraid to threaten my dad and call the humane society but i want to know what I could do to not make this such a big deal.