assault in jail

my son was assault in jail and was in state custody a man can in to his cell and beat him in the face with a sock that had a bar of soap in it, he had to be taken to the hospital and have xray done and had to have surgery done on his nose the jail charged the man that did this and now my son is getting the bill for all this mt question is if he was in state custody and was suppose to be protect by the jail and they let this happen and also the man that did this was suppose to be on somekiond of med for his mental health and he was not taken it should the jail be responable for the bill it is on my son credit report and he had good credit it around 4.000and he is still instate custody and will be getting out soon

The jail normally has to pay that bill yes. See a lawyer if need be.