H.F. Sills was the mystery man of the O.K. Corral hearing. Sills was visiting Tombstone at the time of the shootout and had no connections to either side.
Sills was at the empty lot prior to and during the fight. His testimony confirmed that the Cow-boys had threatened the lawmen just before the confrontation—and that everything that Virgil and Wyatt Earp said about the event was accurate. A tough cross examination couldn’t budge his story, which was key to the eventual acquittal.
After the hearing, Sills left town and disappeared into history.