He was "the toughest marshal" working the Indian Territory on behalf of Judge Isaac Parker, the real-life judge of the United States District Court for the Western District of Arkansas (having criminal jurisdiction in the Indian Territory, as the bailiff repeatedly announces in both films). When Cogburn goes to court in "Rooster Cogburn," it shows that Cogburn shot a total of 64 men in eight years, killing 60 (by the film's end, it was 70 shots, and 66 killed), all of whom he claimed to have killed in self-defense, in the line of duty, or fleeing justice.
He was "the toughest marshal" working for Judge Isaac Parker in the Indian Territory, who had authority over crimes in that region. When Cogburn appears in court, it is shown that Cogburn fired a total of 64 men in eight years, killing 60 (later 70), all of whom he claimed to have killed while defending himself or others.