A New York Republican, Dr. Cooper attended a dinner party in February, 1804 during which Alexander Hamilton spoke forcefully and eloquently against the Federalist plan to nominate Aaron Burr as its candidate for the New York governor's office. Cooper later wrote a letter to Philip Schuyler, a New York politician and Alexander Hamilton's father in law, in which he made reference to particularly "despicable opinion" Hamilton had expressed about Burr.
The letter, when published in a New York newspaper called the "Albany Register", was tame compared to the other attacks Burr had incurred in the press. Still, Cooper's letter proved the last straw in the ongoing rivalry between Burr and Hamilton.
When Burr read the letter weeks later, after being crushed in the governor's race, he was enraged by Hamilton's alleged remarks. Burr, who was also eager to regain a place in the national spotlight, challenged Hamilton to a duel. If Burr sought fame in this contest, he gained only infamy; the duel ended in Hamilton's death and Burr wanted in two states for murder.