Investigators say it happened around 10 a.m. during a controlled pheasant release at the 9 Bar Ranch just outside Decatur.
Nine-year-old Callen Little, his parents and his grandfather were in a hunting stand.
At some point, Callen left the stand.
The grandfather accidentally shot the boy in the chest as the birds were released.
"He'd left the stand for some reason and then the birds were released and when they shot, they shot into the direction where the boy was, and he was struck in the chest," said Wise County Sheriff David Walker.
Sherriff Walker says the ranch has had an impeccable safety record.