An eight-year-old boy shot his grandmother dead after playing the violent video game Grand Theft Auto IV.
Marie Smothers, 87, was shot in the back of the head as she watched television in her mobile home in the town of Slaughter, Louisiana.
The grandma, who was helping to look after the boy, was pronounced dead at the scene at the Country Breeze Mobile Home Park.
The child told investigators that he accidentally shot her while playing with a firearm, a .38 calibre handgun that belonged to Marie.
East Feliciana Parish District Attorney Samuel D'Aquilla said: "He thought it was a toy gun."
The boy, whose name was not disclosed, is not charged with a crime and has been released to his parents.
Louisiana law prevents children under 10 from facing criminal charges, on the assumption that they are not mature enough to have criminal intent.
The boy did not appear to have murder in mind when he pointed the handgun at the back of 87-year-old Marie Smothers' head and pulled the trigger last week, D'Aquilla said.
"He doesn't know that if you point a gun at somebody, it kills them and they're gone forever," D'Aquilla said.
"It's not because he is a cold-blooded killer and he did this to kill his grandmother."
He added that the boy was 'really shaken up' by what happened.
The authorities pointed out that the child was playing Grand Theft Auto IV before the fatal shooting. The game is rated "M" for mature audiences, is recommended for ages 17 and above, and has been associated with encouraging violence.
Neighbour Johnnie Scott said: "Where did she have the gun? Where did he see the gun, was it in his eyesight? That's the thought that goes through my head."
Police said that, prior to the shooting, Marie was close to her grandson.
"The victim and the juvenile had a normal, loving, relationship and even shared the same bedroom," a spokesman said.
Child psychologist Kristopher Kaliebe said access to a violent video game may encourage aggressive behaviour.
He said: "From a behaviour therapy perspective, I would say that's practising.
"When you have a video game that is shooting at a human being, that is practising shooting at a human being."
The child is currently being looked after by his parents.