I would suggest watching a deep touching war movie. Like Saving Private Ryan, or Saints and Soldiers.
Something with a lot of action, a lot of death, especially of those they care about, but also having to move on to survive. They give some time to the characters, sometimes not much, but you know those characters aren't forgotten to the others. Even if it's little things, like in Saving Private Ryan. ETA: Black Hawk Down, the leg shot. Good scene.
He takes the blood stained letter and in a later scene is recopying it to a clean sheet of paper because he doesn't want the soldier's father to see his son's blood on the paper.
You can also try talking to a soldier who has served in a war. Ask him/her about a situation where a brother in arms died, ask them to just tell stories even. You'll get the reactions you are looking for.
I would have some lingering over the body, even if it's from a distance. Take something personal with him, a memento, or have an earlier scene where the dead man gave his friend something important. This will allow him later reflection on past events, and remind the reader what kind of presence that particular character invoked in the story and on your main character.