CONCORD — You can only speculate about the last moments of a Vietnam soldier killed in action. Imagine the choking clouds of dust followed by a heavy pattering of rain, those adrenaline-filled heartbeats of a soldier, ready to do what his country asked him to. Imagine that soldier, fingering a lucky Zippo lighter in his pocket, another touching a cross nestled around his neck, all of them checking their weapons. They take fire, three don’t make it out. Things similar to these may have happened during the last moments of Sgt. First Class Donald “Donnie” Monroe Shue. Shue, an Army...