What happens legally when a 13 year accidentally shoots and kills her brother

[snailslime]

I'm writing a story and a key moment in my protagonist's backstory is when she was thirteen and accidentally shot her twin brother in the head during a hunting trip with their father. I was thinking about having her get sent to some sort of juvenile correction/mental health facility until she turns eighteen, but I wasn't sure if this was accurate to how United States law works regarding these types of situations. Also, would any sort of serious legal repercussions be unrealistic given this would be something that happens within the family, and if so, would it work better if the brother was instead the child of a family friend? Any info would be helpful!