In the Lincoln County Cattle War of the 1880s, two large ranches were pitted against one another for control of range land. Billy was a cow puncher on the losing side. The law in Lincoln County, which was in the hands of the winning side, wanted Billy and several of his cohorts brought in for trial. He eluded capture, killing several men in the process. Eventually he was taken prisoner and put in a cell in Las Vegas, New Mexico, from which he escaped after tricking the guard, a deputy, and shooting him dead. He fled to a friends ranch at Fort Sumner where he hid out until tracked there by his friend Pat Garrett, who hid in a darkened room until Billy entered and heard the hammer of Garrett's pistol click back. Billy said "quien es?" several times, and then Garrett shot and killed him. Billy Bonny was eighteen years old.

It is clear that Billy, whatever is said about his reasons for killing several men, was proud of the notoriety it gave him, and he himself carved 23 notches on the stock of his Winchester. At this point, a pardon would seem to be superfluous.