Police haven't said what sparked the argument that led to the shooting death of Austin Riddell in Connoquenessing Township, Butler County on Friday.
State police say Riddell's 76-year-old grandfather, Larry Karnes, shot Riddell in the chest with a .22-caliber rifle. Butler County Deputy Coroner Denny Trzeciak says Riddell was a large man and he found it unusual he was killed by a single wound of a small-caliber firearm.
The cause of Riddell's death is pending the results of toxicology tests.
Karnes is charged with criminal homicide. It's not clear if he has an attorney.