And as far as the way that the soldiers are speaking in the video, which is pretty callous and joking about what's happened ... that's a coping mechanism. I'm guilty of it, too, myself. You joke about the situations and what's happened to push away your true feelings of the matter.
There's no easy way to kill somebody. You don't just take somebody's life and then go on about your business for the rest of the day. That stays with you. And cracking jokes is a way of pushing that stuff down. That's why so many soldiers come back home and they're no longer in the situations where they have other things to think about or other people to joke about what happened ... and they explode.