Is it just a boy thing?

I have noticed a pattern in my children's stories that they tell.  In every single story, some one gets hurt or dies.  They do not watch the news or any older type cartoon.  My tv is on Noggin whenever it we turn it on.  We closely monitor what they watch because they are still so young.  We have been trying to get them to tell us more stories lately, and we try to do silly stories but somehow the purple fish with green polka dots gets ran over by a car.  My 6 year old son has his own writing notebook that he can write in and draw in and the other night I just picked it up and read his recent story.  It went like this.  On Sunday, it was Christmas.  John, Evan, and Elishah gave Santa some milk and cookies.  Santa gave me a blue scooter and I love it.  (at this point I am thinking that this is gonna be a cute story, but then I continued)  On Monday, the day after Christmas, Santa was killed by a fox.  Poor Santa.

When I asked my son why Santa was killed by the fox he told me that his sleigh broke down. 

I wonder if I should be worried about this or if its just a boy thing?