Henry Augustus Weeks enlisted in Company G, 22d Massachusetts Volunteer Infantry on 9 September 1861. He went with the unit to Virginia, where he participated in the Peninsular Campaign. Part of the time he served aboard a hosital ship. While enroute back to his unit from the hospital ship, he ran into a Confederate patrol. After engaging the patrol, and allegedly killing several, he was himself shot in the right wrist and taken prisoner - 27 June 1862. He was sent to Libby Prison in Richmond, VA, but was exchanged on 19 July 1862 - a quick turnaround and a lucky circumstance, since Libby, like most Civil War prisons on both sides, was a horrible place.
Upon exchange, he was transferred to the Hospital Ship Vanderbilt and then to the hospital at David's Point, New York (probably the DeCamp Hospital on David's Island, NY, the largest Union hospital). He was finally invalided out due to the wound on 10 Feb 1863.
He would have been lucky to have not lost his arm completely, having been shot with a soft lead bullet. The wound apparently crippled him for the rest of his life.