Has your friend been back to the doctor to report his symptoms? The first thing I thought of was a brain tumor because that's how my dad did before he was diagnosed with 3 malignant brain tumors (he never had skin cancer). Not meaning to scare or worry you, but that's exactly what it reminded me of when I read your post. One of the things the doctors quizzed the family on was a drastic change in behavior, hostility or sudden unexplained changes in his mood, repetitive statements or movements were some of the things they asked us about. Fortunately, the only thing any of us could tell them was he would get headaches and sleep for hours. We later found out that when he rested it reduced the pressure he was feeling in his head. My mom later confessed he was acting strangely and always complained of being tired.
Have you suggested that your friend go and get a check up or have you talked to him about his behavior? Is he on any medication that you know about?
Take Care...Scarlett