Henry had to witness firsthand the sight of his friend, Jim, dying. When Jim asked him for his help in keeping Jim off the road if a battery comes along, Henry was unable to give his assurance of help. He even was not able to go to Jim's body when it gave way and Jim died. All Henry was able to do was stand and watch everything unfold before his eyes.
He had thought of Jim as invincible and seeing him die made Henry question his mortality. He thought of himself as brave and a team player but when his courage was tested, the first thing he did was run away from trouble to save himself, leaving his comrades to their fate.