An expert marksman, Dickinson was shot in the chest by the future president due to a protracted disagreement which originated in an incident involving a horse which Jackson owned.

[1] He studied law under U.S. Chief Justice John Marshall, who wrote formal letters of introduction and recommendation for his student.

Dickinson owned a house in Maryland for three years before moving to Tennessee, where he became a successful horse breeder and plantation owner.

A history of Caroline County published in 1920 describes Dickinson as "brave and reckless, a trader in blacks and blooded horses, and reputed to be the best shot in the country.

"[2] According to a blurb in a New Castle, Pennsylvania newspaper in 1883, Dickinson had a place in Preston, Caroline County, Maryland, but "he sold it in order to embark in negro trading.

[3] An 1882 description of the farm, published in a Denton, Maryland paper reads, "The dwelling, which is quite large and contains many rooms, is much decayed and badly in need of repairs.

The old barn, built and used for a temporary jail in which slaves were confined before being sold south, is a picture of desolation, but still retains in its massive timbers the staples and ringbolts to which many a hapless mother was chained after bidding a last sad farewell to her children before leaving them for ever.

The sequel to their one-time friendship and business relations, which did not survive the exigencies of Tennessee politics and social life, was the duel on the Red River in Kentucky in which Dickinson fell.

"[2] An acquaintance of 10 or more years, then, may be the basis of claims made by Jackson in a letter written after the duel: "...for the present it will only be observed that the deceased, could not be called a Citizen of this state—that he was engaged in the humane persuit of purchasing Negroes in Maryland and carrying them to Natchez & Louisa and thus making a fortune of speculating on human flesh—can it be that because he was engaged in this human trafic, he commands this unusual respect from his honour the Judge, the two Doctors, and the petyfoging lawyer..."[6]: 106  Jackson was an interstate slave trader himself—although he always denied it publicly—but with apparently unabashed hypocrisy, he repeatedly accused his enemies of participating in the trade using the moral argument as a bludgeon when it was convenient for him.

According to the pre-race agreement, if a horse was unable to race, a forfeit fee of $800 would be paid to the injured party, in this case, Jackson.

The affair continued, with more insults and misunderstandings, until Dickinson published a statement in the Nashville Review in May 1806, calling Jackson a "worthless scoundrel, ... a poltroon and a coward".

John Coffee, a friend of Jackson's, had fought a duel earlier in the year with one of Dickinson's associates, and there were larger political and sporting interests involved.

Jackson responded in the same newspaper, claiming that Swann was a "lying valet for a worthless, drunken, blackguard", meaning Dickinson.

[11]: 138–139 This was the last straw for Dickinson, who, after he returned from New Orleans in May 1806, published an attack on Jackson in the local newspaper, calling him "a poltroon and a coward".

Dickinson left Nashville the day before the duel with his second and a group of friends, confident, even demonstrating his shooting skills at various stops along the way.

Jackson's pistol stopped at half cock, so he drew back the hammer and aimed again, this time hitting Dickinson in the chest.

While Jackson could easily have been incapacitated by such a wound, an unconfirmed account later claimed that while conversing with a friend on his deathbed he stated, "If he had shot me through the brain, sir, I should still have killed him.

[16] Caroline County, Maryland has a historical marker asserting that Dickinson is buried there: "Body returned here by Truxton faithful Negro servant.