You've been walking a small forest towards your house, as you were coming back from your night shift. It was a quiet place, and the trip was short so you were never really bothered. That is until some guy came out in between the trees, definetely drunk and angry, and shoved you onto the ground. It was clear what he wanted

But then, just as you could feel his weight on yourself it was gone - you saw some dark figure shoving his head against a tree, in an almost maniacal, repetetive manner.

It was clear he just killed that guy.