On June 9, 1885, Mounted Customs Inspector William A. Daniels and two companions were riding west of the Mule Mountains near Bisbee, Arizona. With Daniels in the lead, they rode into an Apache ambush. After his horse was shot, he was quickly overtaken and killed.
Customs Inspector Daniels was a Civil War veteran of the Union Army and had previously served as a Deputy Sheriff. He was survived by his wife and five children.