The boomerang seemed to have a mind of its own

I was playing with my fantastic new boomerang,I threw it with all my might,and then it did the most strange thing,it bounced of the bench over the next door neighbours fence,then I heard a loud screech,then it came back to me and I caught it in my hand,the boomerang seemed to have a mind of its own.It all seemed to happen at once,the girl came over with an ice pack on her head,complaining that she was in the middle of practicing gym when something hit her on the head.I glanced down at the boomerang and wondered what had just happened!