As a member of what the U.S. government called the "SI band", Kid developed important skills and became a famous and respected scout and later a notorious renegade active in the borderlands of the U.S. states of Arizona and New Mexico in the late 19th and possibly the early 20th centuries.

A few years later, in 1881, the Kid enlisted with the U.S. Cavalry as an Indian scout, in a program designed by General George Crook to help quell raids by hostile bands of Apache.

He worked on assignment both in Arizona and northern Mexico over the next couple of years, but in 1885 he was involved in a riot while intoxicated, and to prevent his being hanged by Mexican authorities, Sieber sent him back north.

Kid married into another important family, becoming the son-in-law of the prominent "SL band" chief Eskiminzin (Hashkebansiziin – "Angry, Men Stand in Line for Him", 1828–1894), his wife was possibly Nahthledeztelth.

On June 1, 1887, Sieber and Lt. John Pierce confronted the scouts involved in the altercations, and ordered them to disarm and comply with arrest until the incidents could be handled properly through investigation.

They were freed, but in October 1889, Apaches in the area enraged by their release were able to force the issue of new warrants, and again the Kid was on the run.

Militias, bounty hunters, and U.S. Army soldiers cooperated over the following months in a manhunt for the escapees, all of whom were eventually recaptured except for the Apache Kid.

During an 1890 shootout between Apache renegades and Mexican soldiers, a warrior was killed and found to be in possession of Reynolds' watch and pistol.

In 1899, Colonel Emilio Kosterlitzky, of the Mexican Rurales, reported that the Kid was alive and well and living among the Apache of the Sierra Madre Occidental.

In his book, Cow Dust and Saddle Leather (1968), Ben Camp relates in detail his knowledge of the last days of the Apache Kid.

In it, the author describes the scene he witnessed as a 17-year-old, how Billy Keene, a member of the posse, actually had the head of the Apache Kid in Chloride, New Mexico in the year 1907.

The chapter describes how, starting September 4, 1907, the posse split up and tracked down the Apache Kid in the San Mateo Mountains.

Following a raid on the Mormon settlement in which Apaches stole food, livestock, and supplies, ranchers Martin Harris and Thomas Allen tracked the raiders to their camp.

The inventory included: French field glasses, a bow and quiver of arrows, moccasins and leatherwork of fine craftsmanship, a Colt revolver with a pearl handle, a rifle, a belt filled with .45-70 cartridges, a feathered war cap with silver and turquoise adornments, two crosses, one Catholic and one Masonic, a medicine belt with roots and herbs.

The leader's body was buried alongside the woman and child, with Mexican officials later verifying that the deceased were Apaches.

Edgar Rice Burroughs, future creator of the Tarzan tales, was a member of the 7th U.S. Cavalry while they were "chasing" the Apache Kid in 1896 Arizona.

According to local residents,[6] the body was not buried and the bones and shreds of his clothing lay scattered about the site for some years, with people taking some as souvenirs.