How to stop it?

I am a young mother (30) of 1 son who is 4 & I see these news stories about teens either being caught planning to take fire on their school peers or teens just killing their school peers. What's going on here? It's becoming a trend to kill. Why? I recall an event in high school where one of my peers killed another that was supposed to be his friend & someone who was a really nice & genuine person so it's nothing new but it's certainly getting worse. Are we being too liberal with our children? At that age I understood that I was only one person amongst many others who too were humans and even if I hated them I could never fathom killing them. So what's your take on this & could yours or my child fall into this way of thinking? I must add that although I was raised to believe in God & now have my own thoughts regarding religion; neither would have led me to believe more than the fact that people are people & no matter what it's not up to me to decide who lives or dies. I am just here.