Divergent VS. Hunger Games

I have read all of the Hunger Games (Hunger Games, Catching Fire, and Mockingjay) by Suzanne Collins and really enjoyed them.  I  just finished Divergent by Veronica Roth and can say I liked that too.
But what I want to know- what is with all the guns and killing?  I understand teen novels tend to have more angst than say, adult fiction. Both had a bit of that in them.  But the whole teen as killer thing seems to be a new trend in Young Adult Fiction.


I've read other series (My Fair Assassin by Robin LeFever, Graceling by Kristin Cashore, The Mortal Instruments by Cassandra Clare)-all with strong female leads, who also happen to be deadly.


Earlier series like The Enchanted Forest Series by Patricia Wrede or Song of the Lioness by Tamora Pierce had kick-butt heroines but violence was minimized. Both were written in the 1980's so that may be the difference.


I just wonder if I am just showing my age or has the world become so desensitized to violence that it is prevalent in today's teen stories as well as adult. Has literature written for young teen males always had that edge to it (sorry- I was raised in the 60's and 70's but in a conservative small town.)  What am I missing? 
I know teen girls want to be/deserve to be portrayed as strong, independent people. I get that and like that. I like that girls can solve problems. But when a girl has to shoot a classmate in the head to save herself and "the world as she knows it"-is it the right thing to do? 


I would love to hear what others think of this trend.