The police chief said the answer might not ever be known.
Jackson County Coroner Dr. Gregory Hawker said investigators don't know whether the shootings in Jackson in southern Ohio were a murder-suicide, a suicide pact or an accidental shooting followed by suicide. Authorities say each boy had a single gunshot wound to the head.
"You want to think it was an accident," Hawker said, adding that there's not enough evidence yet to draw any conclusion.
"There was no sign of a struggle," Hawker told The Associated Press. "The younger boy was just sitting in a children's chair, sitting there like he was watching TV."
He said only two bullets were fired, and two casings were recovered along with a .44-caliber handgun. The gun belonged to the boys' grandfather, Police Chief Carl Eisnaugle said Friday. Investigators don't believe anyone else was involved.
Hawker said state investigators have taken the older boy's computer to look for clues to what might have led up to the shootings.
Eisnaugle said there might never be an explanation.
"Whether or not it's an accident would be extremely hard to determine," Eisnaugle said. "I don't know if we'll ever know.
The Franklin County coroner's office in Columbus conducted an autopsy and the state Bureau of Criminal Investigation is analyzing evidence from the scene. Hawker said final results probably won't be known for six weeks or more.
The shooting happened Wednesday in an upstairs bedroom at the home of the boys' maternal grandparents. Police say the boys, Austin Wiseman, 12, and Blake Campbell, 9, lived at the home.
Authorities said the grandparents had gone out to take care of some personal business but talked to the boys by phone at about 10 a.m. Wednesday. It's believed the shootings happened at about 11 a.m. Property records show the owners of the home are James and Deborah Harris, whom neighbors identified as the boys' maternal grandparents.
Hawker said the bodies have been released to a Jackson funeral home that was working with the family on funeral arrangements.
"They all were in deep mourning and shock," Hawker said of the boys' relatives.
A man at the home who identified himself as an uncle said he no comment Thursday afternoon.
Shirley Causey, who said her grandson was a cousin and frequent playmate of the older boy, said Austin was polite and protective of his younger half brother. She also described the grandparents as very loving.
Jackson is a city of about 7,000 people in mostly rural Appalachian Ohio, 65 miles south of Columbus.
Associated Press writers Mitch Stacy in Columbus and Lisa Cornwell in Jackson contributed to this report.
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