What do we do with grandpa?

Grandpa is eighty and has dementia. He has turned from the gentle soft spoken man we've known all or lives to a man spirited, cursing hateful person whom no one can handle. He screams, he yells he accuses everyone if stealing from him. He has attacked my sister. He tries to damage the furniture and now he leaves the house and wonders around until someone brings him home. We don't know what to do at this point. His doctor is no help.