I believe that the Sapp brothers were mentioned on a ranger led battle walk this past weekend at Gettysburg. The ranger (John Heiser) had a photo of a Judson in his officers uniform, and had a similar, but not identical, story:

The ranger said Sapp took shrapnel to the thigh during the initial stages of the brigade's advance. Sapp bound his wound and fought on, but the wound festered by the next day. His brother stayed with him, both were captured after Lee's retreat, and Judson died of the infection that set in.

Looking at the dates on this thread, you may be the source of the ranger's information. If not, you might want to contact him.