Did you try killing his bestfriend as a prank aswell?
**Edit: Sorry, I didnt try to come off as mean but you have to understand consequences. He will definitely forgive you but it WILL take time. Even then, it will definitely affect the way he approaches people in the future if you say that he is introverted as he was.
Actually, you should have lied to him instead that some outdside factor cannot keep the relationship going. Like parents dont allow it or something.