Afghan officer kills 6 U.S. service members

I read an article in the Tuscaloosa news titled "Afghan officer kills 6 U.S. service members". A man killed these men in a shoot out, and then got killed himself. I don't understand why this kind of violence happens. I mean, you can be mad at others and not have to kill them. Just because these mean were his enemies, he felt like he had his opportunity to shine, and murdered innocent victims. For what? Because he also died. He got nothing out of it, and he sure isn't a "hero" in my book, he's a bad man.