Army SGT Kills Specialist

So I found this article about a 40 year-old male Sergeant who killed a 28 year-old female Specialist in her barracks room on Fort Carson, CO. They said that she was killed sometime between the 6th and 8th of January.

So it sounds like he chose to kill her when he knew that she wouldn't be expected for work. The 6th was a Friday, so if the SPC didn't have to work again until Monday, no one would come looking for her.
I wonder if they were in a relationship. Plently of people kill others for not wanting to be with them. I can kind of see that. Maybe she realized he was too old for their relationship to really last. Or maybe she cheated on him. Or maybe she realized that he was crazy, as he obviously is. In any case this is such a disturbing event.

The morale of both their units has probably gone way down. Each of them had/have friends and family who have to cope with this. Why is harming someone else even an option? What situation between two people who are both living warrants one killing the other?

Don't get me wrong, I can think of a few scenarios in which I would want to kill someone else, but it involves them killing or seriously harming someone close to me. I have never been in a relationship that ended with my wanting to kill the guy. Punch him in the throat? Sure, but not kill him! Click on the link below for the original news story; this is just my take on it.

Man arrested in barracks death at Colo. Army post