The infamous Western outlaw known as “Billy the Kid” is mostly likely born in a poor Irish neighborhood on New York City’s East Side on November 23, 1859. (Much about his early life is unknown or unverified.) Before he was shot dead at age 21, Billy reputedly killed at least nine people in the American West.

Billy the Kid called himself William H. Bonney, but his original name was probably Henry McCarty. Bonney was his mother Catherine’s maiden name, and William was the first name of his mother’s longtime companion—William Antrin—who acted as Billy’s father after his biological father disappeared. Around 1865, Billy and his brother traveled west to Indiana with their mother and Antrin, and by 1870 the group was in Wichita, Kansas. They soon moved farther west, down the cattle trails, and in 1873 a legally married Catherine and William Antrin appeared on record in New Mexico territory. In 1874, Billy’s mother died of lung cancer in Silver City.

Billy soon left his brother and stepfather and took off into the New Mexico sagebrush. He worked as a ranch hand and in 1876 supposedly killed his first men, a group of Apache Indians, in the Guadalupe Mountains. According to legend, it was not long before Billy killed another man, a blacksmith in Camp Grant, Arizona. Billy the Kid, as people began calling him, next found work as a rancher and bodyguard for John Tunstall, a English-born rancher who operated out of Lincoln, New Mexico. When members of a rival cattle gang killed Tunstall, in 1878, Billy became involved in the so-called Lincoln County War.

Enraged at Tunstall’s murder, Billy became a leader of a vigilante posse of “regulators” sent to arrest the killers. No arrests were made, however. Two of the murderers were shot dead by Billy’s posse, and a worsening blood feud soon escalated into all-out warfare. After Billy’s gang shot dead Lincoln Sheriff Bill Brady, who had sanctioned Tunstall’s murder, Billy’s enemies conspired with the territorial authorities to do away with the regulators.

In July 1878, the rival gang surrounded the house where Billy and his gang were staying just outside of town. The siege stretched on for five days, and a U.S. Army squadron from nearby Fort Stanton was called in. Still, Billy and his gang refused to surrender. Suddenly, the regulators made a mass escape, and Billy and several of the other regulators miraculously managed to shoot their way out of town.

After more than two years on the run, Billy was arrested by Lincoln Sheriff Pat Garrett, a man Billy had previously befriended before Garrett became a lawman. In April 1881, Billy was found guilty of the murder of Sheriff Brady and was sentenced to hang. On April 28, two weeks before his scheduled execution, Billy wrested a gun from one of his jailers and shot him and another deputy dead in a daring escape that received considerable national attention.

On the night of July 14, 1881, Garrett finally tracked Billy down at a ranch near Fort Sumner, New Mexico. He gained access to the house where Billy was visiting a girlfriend and then surprised him in the dark. Before the outlaw could offer resistance, Garret fired a bullet into his chest. Billy the Kid was dead at age 21.