President Garfield: From Radical to Unifier by C. W. Goodyear:
Paunchy with a dense, dark, mustache, Sickles had already made himself infamous as a man unafraid (proud, even) of taking extreme measures if the moment demanded them. As a congressman in antebellum Washington, he had shot his wife’s lover (the district attorney) dead in the street before pleading temporary insanity. It was the first time such a defense had been pulled off in America. But, post hoc, Sickles did not stick to it. “Of course I intended to kill him,” Sickles admitted to friends. “He deserved it.” The murderer-cuckold later became a Union general. While galloping across Gettysburg, he was clipped in the leg by a Confederate cannonball, shredding the limb below the knee. Sickles had the bones collected in a tiny coffin and sent to museum curators. For years to come, he brought friends to pay respects to the shards on display.