He did it in private inside his car talking to someone else. You see violent and tragic death almost daily and you either have to go crazy or have a little gallows humor. It’s childish to expect cops to emote and be somber and mournful about everything among themselves. Same goes for the military.
I think, for some people, they’d rather have dead cops who committed because they weren’t allowed to cope with what they deal with, as long as their virgin ears are protected.