When I am teaching the Penal Code at the police academy, I actually make up a scenario like this to distinguish between Murder, Manslaughter and Criminally Negligent Homicide.
If you shoot and kill someone, it could be any of those which range from two years maximum to 99 years. One of the scenarios is that you were shooting a gun and accidentally hit someone a good distance away that you did not even know was there.
Fortunately this girl appears to be suffering from a minor injury but it could have been a lot worse.