I need some serious advice! A good friend of mine is being beaten by her boyfriend, what should I do?

So, I don't want to be known as the "snitch" of the group, but I don't think this is right, and I'm not sure how to go about the situation. We are young, still teens, but she has a baby and a "baby daddy", who in her words, "Beats the **** out of her." Some others girls get hit, too. I don't know if as bad, but I do know, that something is wrong up there. Why would these girls think it's okay to let their boyfriends hit them? What would you do? Please, this can be someones life in jeopardy!