Now that I had a chance to watch the video.
Who doesn't feel good when they succeed? A soldier's primary job is to kill. Doesn't matter if you are infantry, medic, signal, engineer, etc. everyone's primary job in the military is to kill. When you do your job well you enjoy it and get satisfaction out of doing a good job. Why shouldn't killing feel good if that is your job?
Let us go to home defense. You kill a burglar who was going to harm you and your family to get whatever the burglar was looking for. You feel good you killed the burglar to keep your family safe.
According to this video people who play violent video games and watch human suffering on shows or movies are more likely to kill. What if that person joins the military. This person should be even more likely to kill. Military personnel associated to all this violence early in their life development and are now in the military should have a very high chance of killing a harmless person within their own society.
This 11 year old kid killed someone who did not pose a threat. He just didn't get his way so he killed the person who wouldn't let him have what he wanted. The little girl could had easily of been one of his parents that didn't give him what he wanted or anyone else.
Violent deaths are neither random nor mysterious events. They occur within specific contexts and can be understood in light of the overall events of which they are a part. They are difficult to prevent because they often represent circumstances largely created by people who then react badly to those circumstances.
Homicide and suicide in the military have been less frequent than in civilian life. The circumstances of military and civilian deaths are similar with fact of being greater in number of relating to relationships or communication between people conflict and the notable exception of the lack of drug-related murders within the military. We find no evidence that the lethal violence that is the mission of the military is reflected in the lives and deaths of active duty military personnel.