Allen County Prosecutor Karen Richards declined to charge Stephen Jewel, 66, in the May 2013 killing of his son, Russell Jewel.
On Monday, spokeswoman Robyn Niedzwiecki said the prosecutors office ruled the shooting justified as an act of self-defense. The case had been investigated by the Fort Wayne Police Department.
Russell Todd Jewel, 42, lived with his parents in their home at 5031 Wisteria Lane.
In 1998, a motorcycle crash left Russell Jewel with a head injury and he was never the same, his mother told The Journal Gazette.
His family also said Russell Jewel abused drugs.
On May 29, Russell Jewels behavior was erratic and, after arming himself, his father went to the other end of town to bring Russell Jewel back home. After arriving home, Russell Jewel began beating his father in the familys kitchen. His father had a gun in his possession and as his mother called 911, Stephen Jewell fired the gun, with Russell Jewell on top of him.
Russell Jewel was killed, and his death ruled Allen Countys 20th homicide of 2013.
Prosecutors have yet to rule the police-action shooting of Tavontae Haney in April, or the October slaying of Ricardo Hood who was reportedly trying to burglarize a home in the 300 block of Melita Street.