Please help me before my niece is murdered by her "mother's" boyfriend - there are already bruises all over?

My sister is 20 years old with 2 children. She met a 30-something year old truck driver at work and her life has gone downhill. We suspected that he was abusing her, and we knew her kids weren't being treated right by him. I personally had heard him call them "little f*ckers".

She started acting like a totally different person... scared all of the time and quit coming around us. He moved her 2 hours away and she gave her 4 year old son to her mom to "stay with her for a while". Her mom has been more of a mom to him all of his life though, so that wasn't out of the ordinary. She kept her 2 year old daughter with her.

We hadn't seen my niece in over two months so we begged my sister to bring her to us for a visit. Her boyfriend had his grandma follow her down and follow her back up after she dropped my niece off.

We noticed 2 bruises on my niece's cheeks when she first got into the house. My sister said that she's been "jumping off of counters". My little sister gave her a bath that night and we found more bruises. We found baseball size bruises on her butt and the back of her legs and found other bruises on her forehead, the top of her left ear, both legs and both arms, her back, and her inner thighs - all different colors and sizes, some were old and others were new. Now how does a child get bruises on their ear and inner thighs from falling off of a counter?

We called the police and they came out, took pictures and contacted children services. We asked my niece who hit her and she said "Shawn" (my sister's boyfriend). Her 4 year old brother told his grandma that Shawn had hit him in the face before.

Children services also came and took picture and then contacted the CSP in my sister's county. My niece was place with her brother at their grandma's house. The next day, CSP called and told the grandma that my sister would be picking up her kids and she was not to keep them from her. My sister decided to text message all of us and her boyfriend called to leave voice messages saying that we would never see them again.

I have heard alllll of the stories about kids being hit one time the wrong way and being killed. I don't know what to do. They are so fragile and so precious and the system has failed us all. What can I do? Please help me out... Even if you know any of the websites dedicated to those precious angels that were murdered. Maybe their families can help. Maybe they know people or any way to get anything started. We don't know what to do.

And just a side note, we don't know who the biological fathers of either of them are, so that's a dead end.

Please help.. time is ticking...