The shooting was called in at 11:12 a.m. behind 24 1/2 W. Franklin St., according to Hagerstown police.
The child, whose name was not immediately available, was playing outside with his 7-year-old sister when they apparently found what police believe is a .22-caliber semiautomatic handgun.
Police believe the child shot himself in the chest, Detective Sgt. Jim Hurd said. Police later identified the handgun as a .22-caliber Beretta.
The child was taken to Meritus Medical Center east of Hagerstown, but was to be flown to another hospital, Detective Shane Blankenship said.
Police said in a news release that the severity of the child’s injuries was not immediately known.
“He’s going to be all right,” said a man who identified himself as the boy’s father, but would not provide his name.
Hurd said the gun was not reported stolen and that police were trying to trace the gun to its owner.
Police said there was one bullet in the gun.
A group of people standing behind the building said they did not see or hear anything.
Police said they have no witnesses to the shooting except for the injured boy’s sister.
Police officers searched through weeds in a small parking lot behind 24 1/2 W. Franklin St. looking for evidence.
Amber Sheffler of Hagerstown, a volunteer at Soul Haven on West Franklin Street, said she heard a noise that might have been a gunshot, followed by police and ambulance sirens.
“It’s scary for me because I have three kids,” said Sheffler, who lives nearby. “We walk these streets every day.”
Sheffler and Ronald Crawford of Ray Street in Hagerstown both said they saw the boy being carried into an ambulance.
“I’ll say a prayer for him. God bless him,” said Bob Simpson of Funkstown, who also was at Soul Haven.
“My heart goes out to him and his family,” Sheffler said.
Eugene Smith, a peer advocate at Soul Haven, said the shooting hit close to home for him.
“Yes it did, because I had a son killed in New York by a drive-by shooting,” Smith said.
His 10-year-old son’s murder was never solved, he said.
“It seems like it’s getting pretty close to home” said Pat Ritchie, who lives on West Franklin Street. She said there are a lot of homeless people in that part of town and a lot of drinking in the alleys.
“You just try and stay away from it,” Ritchie said.