You were right to go to the school administrators and, if you feel that your daughter is in danger, you may also want to call Child Protective Services in your area. Let them know what is happening. They can investigate the situation. It could be that this boy is acting out because he has been a victim himself, or because he has been exposed to such behavior in his home, neighborhood or through the media.

As for your daughter, let her know how proud you are of her and that she should always feel safe coming to you in such situations. Consult with the school administrators to see if there are other ways to put some distance between your daughter and this boy. Hopefully, he'll receive the help he needs, but if you think it necessary, you can also request that he not be in your daughter's class next term.