O'Brien was attached to the Tecumseh on 20 April 1864 . He was officially reported lost with her during the Battle of Mobile Bay on 5 August 1864 as reported in Navy casualty lists., . However his rendezvous index card notes he was attached to the U.S.S. Mobile next and deserted in New Orleans on 9 September 1864. He also was a signatory to the 14 August 1864 letter calling shipmate Josiah Conley out for providing incorrect information.
Awards & Memorials
Alternate Spellings of Name
References and Sources Return of the United States Naval Rendezvous, New York, NY for the week ending April 16, 1864
 NARA T1099. An index to rendezvous reports during the Civil War, 1861-1865.
 "Navy Gazette: List of Deaths in the Navy of the United States, reported to the Bureau of Medicine and Surgery, Navy Department, during the week ending December 3d, 1864." Army and Navy Journal, 10 Dec. 1864, p. 253.
 Officers and Enlisted Men who Died in the Active Service of the U.S. Navy 1776-1885