Henry (Heck) Thomas was born at Oxford, Georgia, on 3rd January, 1850. He moved to Atlanta and joined the police department in 1868. Later he moved to Fort Worth where he operated his own detective agency.
In 1886 he went to work alongside Isaac Parker at Fort Smith. It was a region with serious law and order problems and one of Parker's acts was to appoint 200 deputy marshals. He was appalled by the large numbers of these men who were killed by criminals. Parker was determined to get the region under control and ordered the building of gallows that could accommodate twelve men at the same time. In the next 31 he passed the death sentence on 168 men and four women, of whom, 88, all men, were executed.
Thomas left Fort Smith in 1892 and over the next eight years served as a deputy United States marshal. During this period Thomas, Bill Tilghman and Chris Madsen became known as the Three Guardsmen and were largely responsible for wiping out organized crime in Oklahoma. This included the hunting down of Bill Doolin and his gang.
Thomas was paid a large amount of reward money for capturing dangerous outlaws. This resulted in him being wounded six times in gunfights. Later he became city marshal of Lawton.
Heck Thomas died of Bright's Disease on 15th August, 1912.