Burr ran for governor of New York in 1804 with some Federalist support, as well as that of Tammany Hall, but nevertheless lost the campaign, primarily due to the Clinton and Livingston factions. Burr's loss sealed his political doom. At a political dinner for the Federalist Party held in New York, Alexander Hamilton voiced a despicable slur upon the name and reputation of Aaron Burr. What Hamilton exactly said was not printed at the time, but rumors and newspaper reports reached Burr, who wrote Hamilton and demanded an apology. Hamilton waffled in his response, Burr protested in another letter, and after receiving no satisfaction challenged Hamilton to a duel. When Burr and Hamilton met on the dueling grounds of Weehawken, New Jersey on July 11, 1804 Burr shot Hamilton, who fired into the air either as a reflex after being shot or purposely to avoid shooting Burr. Hamilton was rowed back across the river to New York City, where he lingered until the next day and died in great pain. Burr was indicted for murder in New York State, but never prosecuted. After completing his duties as Vice President in 1805, Burr entered into a conspiracy to wrest the lands west of the Mississippi River from Spain; these intrigues included the Louisiana Purchase.
http://www.nps.gov/jeff/lewisclark2/Circa1804/In1804/HeadlinesAaronBurrDuel.htm