WISH-TV reports Marion County Jail officers found the six men punching and kicking 22-year-old Michael Bell in the head and face Dec. 18.
Bell and 25-year-old Jeremy Priel face charges of murder and robbery for the Dec. 12 killings of 21-year-old Jeremy Crane and his niece, Kyleigh Crane, in a home on Indianapolis' far east side.
The victims' family considered Bell a close friend and Kyleigh called him "Uncle Mike."
The six inmates accused of attacking Bell appeared in court Thursday to face misdemeanor battery charges. Court documents say Bell had pain, swelling and cuts from the beating.