I don't know what was said, but apparently George W. Crawford thought his father was being maligned in an anonymous "letter to the editor" published in an Augusta, Georgia newspaper some time in 1827. The editor refused to reveal the author of the political rant – some say it was a woman – which angered Crawford even more.
Eventually, a young lawyer named Thomas E. Burnside stepped forward and took responsibility. Almost immediately, George Crawford, in defense of the his father's honor, challenged Burnside to a duel.
[Burnside] seems to have been reluctant to fight, but at a time when the Code Duello was in vogue, he well knew the consequences to himself and to his political fortunes, should he refuse to meet his antagonist on the field. He, therefore, accepted the challenge and repaired at once to the scene of combat. But, on the night before the fatal meeting…he dispatched the following note to Mrs. Burnside:
…Dear Wife and Mother:
Tomorrow I fight. I do it on principle. Whatever may be my fate, I believe I am right. On this ground I have acted and will act. I believe I shall succeed, but if I do not I am prepared for consequences. Kiss the children and tell them that if I fall my last thought was of them. Yours most affectionately, THOMAS E. BURNSIDE.
Lucian Lamar Knight, historian for the state of Georgia, after writing the quote above about 1914, described Burnside's note as a "pathetic fragment."
The story of the duel was covered in seemingly every newspaper, and they all recounted it just as was published in the 19 January 1828 South Carolina State Gazette [via GenealogyBank]:
Duel – On Tuesday last, Messrs. Thomas E. Burnside and George Crawford both of Columbia county, met west of the Chattahoochee, and exchanged two shots without effect. On the third fire, Mr. Burnside received in the right side his antagonist's ball. He fell and instantly expired. The dispute, it is understood, originated about some publications which appeared last year, concerning Mr. Burnside and Mr. Crawford's Father, Old Peter Crawford. – Statesman & Patriot…
Mr. Knight goes on to describe the aftermath in his book, Georgia's Landmarks, Memorials, and Legends (Vol. II):
[Burnside's] body was interred, with every show of respect, in the private burial ground of Col. Crowell, whose residence was not far from the spot on which the unfortunate man fell. More than two weeks elapsed before Burnside's family received the sad news, which, when it finally came, after so long a period of suspense, almost cost Mrs. Burnside her life; but she rallied her strength for the sake of her children and afterwards removed to Dahlonega, Ga., where she resided until her death.
A grave marker exists for Thomas E. Burnside at the Crowell Family Cemetery in Fort Mitchell, Russell County, Alabama, but I think the date should be January 15, 1828. An obituary for Thomas was "communicated" to the Augusta Chronicle (Georgia) and published in that paper 29 January 1828 [full article at GenealogyBank].
Near the Creek Agency, in this State, on the 15th instant, THOMAS E. BURNSIDE, Esq. in the 34th year of his age.
It is ever a melancholy and affecting duty to record the death of those we respect and esteem…But when they fall into an untimely grave in the prime of manhood, with the rich glow of health upon their cheeks, and in the full promise of future usefulness and fame, the withering shades of grief pass o'er our bosoms like the dark Simoom of the Desert, and the tongue refuses utterance to the overwhelming fullness of the heart. Such was the fall of our beloved and lamented friend, and long will his loss be mourned with feelings of the deepest sorrow and affection.
Mr. Burnside was a native of Laurens District, South Carolina, and came to Georgia in 1817. – He was occupied as a Schoolmaster till 1820, in which year he was married to Miss Catherine Wood, of Columbia County, and six months afterwards commenced the practice of the Law. His extensive abilities as a lawyer and fine talents as a speaker, together with his unwearied attention to the duties of his profession, soon acquired for him a large and lucrative practice; and the unostentatious liberality with which he dispensed the fruits of his industry upon all who needed this assistance, gained him the unbounded love and gratitude of the poor, & the respect and esteem of all around him. – In 1822 he was elected to the Legislature, where he continued as a Representative from Columbia County to the time of his death, and was considered one of its most efficient and distinguished members…But his life was cut short in the midst of its usefulness, & he has left an aged & infirm mother, an affectionate wife, and three small children, together with a numerous circle of relations and friends, to mourn an event which has bereaved them of one who performed all the duties of a son, a husband, a father, and a friend, with a degree of tenderness, affection, and anxious solicitude for the welfare of others, which made him respected, beloved, and admired by all who knew him.