CONNOQUENESSING — The elderly man accused of fatally shooting his grandson during an argument at their home Friday was apparently attacked by the younger man a week earlier, investigators said. Larry Karnes, 76, was injured in the previous assault. And that apparently was not the first altercation between Karnes and his grandson, 19-year-old Austin Riddell, state police said. “There are indicators of abuse in the household,” said Lt. Eric Hermick. However, police would not say if they believe the prior violence might have motivated Karnes to fire a rifle at his grandson about 4:30 p.m. during an argument at their home on Sunset Drive. Butler County Deputy Coroner Denny Trzeciak, pronounced Riddell dead at the scene. An autopsy determined he died of a .22-caliber gunshot wound to the chest. Karnes remained in the Butler County Prison without bail on a general charge of homicide. Police suspect that Karnes and his grandson got into an argument over the defendant's refusal to give Riddell a ride somewhere. According to court documents, Karnes told police that the argument “became heated,” and he went to his bedroom. “The grandfather left to get away and he shut the door,” Hermick said. “The grandson sort of pursued (Karnes).” At some point, Karnes got his .22-caliber rifle and loaded a round into the chamber, documents said. He came out of the bedroom with the loaded gun and confronted Riddell. “According to Karnes, (Riddell) approached him and he backed up and the rifle went off,” a police affidavit said. The bullet hit the teenager in the chest, and he collapsed on the living room floor, police said. Paramedics were called and tried to resuscitate Riddell. Troopers got there and found Karnes and his wife in the house. They also recovered the rifle and a spent shell casing. Police later took Karnes to the barracks and interviewed him. “He was very candid with investigators,” Hermick said. Hermick would not say, however, if Karnes claimed self-defense in the shooting. He also would not say if police believe the prior abuse could have provoked the deadly confrontation. “But,” he said, “we are aware of prior physical altercations between (Karnes and Riddell).” One of those altercations occurred a week before the shooting. In that fight, Hermick said, Riddell “got the better of” Karnes and left him with injuries. A preliminary hearing for Karnes has not been scheduled, a clerk at District Judge Wayne Seibel's office in Evans City said Monday morning. Several neighbors on Saturday said Riddell was a troubled young man, but was on the path to getting his life in order. Neighbor Kim Rivers said Riddell did concrete work over the summer and was excited about having opened his first debit card account. But Riddell had been in trouble before. “It was tumultuous over there. It wasn't uncommon to hear fighting or see the police over there,” Rivers said of the house across the gravel road from her's. She said, “You never expect something like this to happen, though. (Riddell) really was trying. That's what breaks my heart more than anything. I think, deep down, he was a good kid,” she said. Rivers and several other neighbors said Riddell began living with the Karneses as a youth, after his father committed suicide. “Our hearts go out to that family,” she said. Neighbors said Karnes is in poor health after suffering a stroke less than a month ago. The A. Carl Kinsey-Ronald N. Volz Funeral Home in Evans City is handling Riddell's funeral.