Eacker was born to Jacob Eacker, who fought in the American Revolution and served in the New York State Assembly. In 1801, Eacker, a supporter of Aaron Burr, made a speech denigrating Alexander Hamilton. Hamilton's son confronted Eacker on November 21. Eacker called them "damned rascals" so, as was common at the time, they challenged Eacker to a duel. On November 23, Eacker fatally shot the 19-year-old Hamilton in a duel.