Larry McElroy was outside his home in Lee County, Georgia when he fired his 9 mm pistol at the armadillo over the weekend.
The armadillo died from the shot, but the bullet ricocheted off the animal, hit a fence and went into the back door of his mother-in-law's mobile home - a distance of about 100 yards.
Then the bullet went through the recliner where the 74-year-old Carol Johnson was sitting and into her back, 'WALB TV' reported.
"Just the circumstances, just all the way around, the whole situation was unusual," said investigator Bill Smith with the Lee county Sheriff's Office.