I don't think the game had anything to do with it.
IF I'm not Mistaken there is No guns in grand theft, it's all Driving,
unless they made a bank Robbery version.
The Boy & the grandmother shared a Bedroom ?
Not sure that is Normal, even at 8.
if it had been an 8 year old Girl & Grandfater
what I'm saying would be obvious
The gun should not have been in her purse & Loaded ,
It should have at least had a trigger Lock on it at Home.
I blame the Grandmother & am glad the DA realized the Kid was Innocent
of all but being a Kid & making a mistake.