As far as I know this Yates is not a relative. I found this while searching for Yates family members in old newspapers.
Pack Horse Shoots Rider
Cave Creek, Ariz. - Hubert E. Yates, 29, Phoenix, was shot by his horse on Sunday. Yates was unsaddling a pack-horse when it kicked his revolver from his holster, causing the gun to fire. Deputy Sheriff Lewis Forman said the bullet hit Yates in the leg.
Newspapers.com; Clipped April 26, 2015