Complex sentence: He later worked as a range detective, and developed a considerable reputation as a gunman, and in September of 1877, Higgins killed cowboy Ike Lantier, whom he caught stealing cattle, after Lantier drew (a gun) on him.
Split into simpler sentences: He later worked as a range detective and developed a considerable reputation as a gunman. In September of 1877, Higgins killed cowboy Ike Lantier, whom he caught stealing cattle, after Lantier drew (a gun) on him.