Carly Gregg, a 15-year-old, was sentenced to life in prison
She was convicted for shooting her mother in their home.
Her stepfather described her as a "sweet girl" before the incident
Gregg appeared mentally distressed, screaming like she had seen a demon.
She did not seem to recognize her stepfather during the shooting.
Video showed her hiding the gun and shooting her mother.
After the murder, she invited a friend to see the body.
Gregg's mental health was a key focus during the trial
Her lawyer argued she was suffering from psychotic breaks.
Experts testified she was aware of her actions and competent for trial.