This is not any first incident that resulted in death of innocent kids, while playing with weapons kept at home for self defense. These kind of accidents happen too often in USA. A five year old girl in Detroit shot herself with a self defense intended revolver and lost life after getting severely injured. 

Maria Davis was playing at her grand mother's residence and happened to find a revolver under a pillow.

She accidentally shot herself while playing with it and doctors declared her dead at hospital. Her grandmother was busy with household work while Maria and two other kids were playing. 

Police were investigating into it for carelessness of old lady and why she left her revolver loaded and unlocked. Fortunately, the other two kids playing with Maria were not injured.

SOURCE : GULTE