The boy was alone in a car while his mother was shopping when the shot was fired, reports Sky News. According to the mother, her son must have found the loaded weapon under the driver's seat.
Monday's shooting in the city of Lehi occurred barely two weeks after a boy died under similar circumstances in the state.
A five-year-old in Santaquin, south of Salt Lake City, found a pistol at home and fired a shot that hit himself.
Utah has no laws that allow prosecution of those who leave loaded weapons lying around. Nor are there laws regulating how weapons should be stored.
Everyone over 21 is allowed to openly carry loaded weapons in the state, without a permit. No permits or controls are needed to buy weapons either.
