How to prove unfit

My grandson resides with his mother. My son is the father. This past weekend I got my grandson and he had been shot in the face with a BB gun, he is not even 2 yrs old. I am livid. Social services has been called and they are investigating. The mother informs me and my son that since social services has been contacted, neither of us can see the baby. There is no custody agreement drawn up and my son pays support. What can myself or my son do to get custody of our lil one?

Your son should be in contact with social services directly to get involved in the investigation.