Who is Clarence Risher from Rogue Warrior and what is their importance?

Clarence Risher is a tall, young member of Richard's second unit in Vietnam. He is characterized by Richard as being emotionally immature. This gives the reader some forewarning of what happens to Risher, who is shot by a sniper. Risher is running in the middle of the street in the battle of Chau Doc, refusing to keep himself under physical cover.