The mother was transported to a hospital in critical condition, the police said in a news release.
Police responded to a call of shots fired at USA Stadium in Millington, where the University of Memphis and University of Tennessee at Martin were tied 2-2 in the first inning during the annual Babe Howard Baseball Classic. About 2,000 fans were present at the game, police said.
The game was suspended after what UT-Martin called a “fan emergency.”
The World War II-era Jeep was part of a veterans appreciation day celebration, and the boy found the gun inside. The weapon belonged to Charles McFarland Jr., 76, who was charged with reckless endangerment and later released on bail, police said.
Names of the mother and child were not released.
“Secure your weapons,” Dunbar said, NBC News reported. “Everybody’s got a right to carry, if they got a carry permit, but you need to use common sense and secure your weapons.”
McFarland could not be reached for comment. Public records under his name matched addresses for a gun store and military museum in the neighboring town of Atoka.
Photos of the museum posted to TripAdvisor.com show children atop World War II and Vietnam-era vehicles and posing from behind M-60 and .50-caliber machine guns.
A woman commenting the police department’s Facebook statement said McFarland is a “sweet man” whose museum delighted her children.
“I agree that Mr. McFarland should have used more thought to his actions but why aren’t we ever holding parents responsible for the supervision and training of the child?” she wrote. “I hate this for Mr. McFarland to be made out to be such a bad guy. He is so kind and thoughtful.”