According to a brief statement by the Lyon County Sheriff's Office, 3-year-old Amanda Marquez died at about 8:03 p.m. at Washoe Medical Center in Reno.
Amanda was shot through the forehead by her 14-year-old brother inside their Fortune Drive home, according to the Sheriff's Office.
Family members said the shooting was accidental.
She underwent brain surgery on Tuesday night and was listed in critical condition at the hospital Wednesday and Thursday.
When authorities were originally called to the home late Tuesday night, the little girl was alert and conscious, even though the bullet passed through her brain from front to back.
The Lyon County District Attorney's Office will decide if charges are to be filed against the boy, who told deputies he thought the gun was unloaded when he pulled the trigger in the house.
Patrol cars and news crews invaded the quiet neighborhood two miles east of Dayton after the 7:30 p.m. shooting on Tuesday.
At first, residents were worried after hearing initial reports that there was a drive-by shooting at the green home with yellow trim.
Jarad Monzello, 15, was outside on the street as police investigated the incident.
"The son of the man who drove me home from church said he heard a firecracker go off," Jarad said.
The father originally told deputies Amanda was sitting outside when someone drove by and shot her.
However, after examining the scene, investigators concluded that the shooting had not occurred in the yard and pressed the boy and his father for more information. That is when they learned the boy shot his sister and there was no drive-by shooting.