Shooting the Moon by Frances O'Roark Dowell

Why does Jamie's brother send letters to her parents, but rolls of film to her to develop? Doesn't he know she wants to know what is really going on in Vietnam? Both have grown up in the army since their father is a Colonel. But as she developes the films, it is clear that the old saying that a picture is worth a thousand words has new meaning. What is her brother trying to tell her that even soldiers can't really put in words? How will that help her when his tour of duty is cut short by the worst news a family can hear? Can she help another soldier from ending up like her brother?