The individual(s) responsible for this heinous crime will be punished, in one way or another. The police know who did this and it is only a matter of time. Meanwhile, the individual, while they may think that they got away with it, it is only a matter of time. Maybe the nightmares have not started, but they will. When they do there will be no hiding. Remember you friends when you are setting in the court room. Remember how they said that they would keep your secret as they testify against you for immunity.
Bad dreams...when you wake up from those bad dreams and you hear the door to your room opening, pray that it is the State Patrol and not the County Sheriff. All sorts of accidents can happen at the county level and I assure you they can be covered up real well. Your chances of survival, turning yourself in at the State Patrol office are much greater than waiting for some hotshot detective coming to your home. There are other options, someone else could find out what you did. Who knows what would happen in that situation?
Turn yourself in before the unknown happens, the State Patrol office is the safest place for you.