He died in 1900 after slitting his throat with a razor. Before his suicide, he murdered his wife and two children with an ax. His problems with mental health were evident years before, as he accused and fought with his teammates, who hoped he would not return to the team after 1899. He had grown paranoid that assassins were trying to kill him and would disappear for days at a time. In a game on October 9th, Bergen had to be pulled when he began dodging his pitcher's pitches because he was avoiding knife thrusts from an invisible assailant trying to attack him. He was prescribed medication to help his condition, but refused to take them, believing them to be poison.
He was the brother of Bill Bergen.