After the war, the family engaged in several business ventures in addition to farming that failed to prosper; young Duncan tried his hand at running a small saddler's shop.
However, most of his duties were rather mundane, ranging from arresting drunks and minor criminals to controlling the city's large population of feral dogs.
Because Hardin had considerable support from family and friends, the Texas Rangers' strategy involved collecting information through undercover detectives.
Continuing his undercover work there, Duncan obtained more detailed information about Hardin's whereabouts; he was on a gambling spree in nearby Pensacola, FL.
The ambush included Escambia County, FL, Sheriff William Henry Hutchinson, Deputy A. J. Perdue, some recently deputized citizens, and Texas Rangers Duncan and Lieutenant John Barclay Armstrong, who was in charge of the overall operation.
Guarded by Duncan and Armstrong, Hardin was transported by train back to Texas to stand trial; he served 17 years in prison for his crimes.
Duncan's activities as a bounty hunter brought him into contact with the rougher side of Dallas society—the saloons, brothels, and gambling establishments.
[4] However, changing times on the Texas frontier ultimately forced Duncan to seek more mundane forms of employment; later in life he worked as: Dallas Sanitation Inspector, general laborer, carpenter, hotel clerk, and as watchman for the Corps of Engineers.
On November 16, 1911, at the age of 61, Duncan lost control of his automobile (a Brush Runabout) on a rough road south of Dallas, and died from sustained injuries or perhaps the loss of his breathing tube.