Wild Bill Hickok - Wikipedia

On July 21,1865, in the market square of Springfield, Missouri, Wild Bill Hickok shot and killed Davis Tutt in what is regarded as the first true western showdown. From the article:

While in Springfield, Hickok and a local gambler named Davis Tutt had several disagreements over unpaid gambling debts and their mutual affection for the same women. Hickok lost a gold watch to Tutt in a poker game. The watch had great sentimental value to Hickok and he asked Tutt not to wear it in public. "They initially agreed not to fight over the watch, but when Hickok saw Tutt wearing it, he warned him to stay away. On July 21, 1865, the two men faced off in Springfield's town square, standing sideways before drawing and firing their weapons. Their quick-draw duel was recorded as the first of its kind.[25] Tutt's shot missed, but Hickok's struck Tutt through the heart from about 75 yards (69 m) away. Tutt called out, "Boys, I'm killed" before he collapsed and died.[26][27]

Two days later, Hickok was arrested for murder. The charge was later reduced to manslaughter. He was released on $2,000 bail and stood trial on August 3, 1865. At the end of the trial, Judge Sempronius H. Boyd told the jury they could not find Hickok acted in self-defense if he could have reasonably avoided the fight.[notes 2] However, if they felt the threat of danger was real and imminent, he instructed they could apply the unwritten law of the "fair fight" and acquit.[notes 3] The jury voted to clear Hickok, resulting in public backlash and criticism of the verdict."