Here is my writing.
In my opinion, it is okay to kill a child when he/she is doing evil things. I oppose treating children as innocent victims just because they are underage. Indeed, some children commit crimes or being used by criminal offenders for they know they will not be accused any charge.
In the situation of the video, I believe I would do the same thing as the police: shoot the little girl. The girl might be innocent, however, what she did were hurting other people, and she needs to take the punishment.
One of the worst situation soldiers facing is armed children.
The casualties that caused by armed children are as serious as adults.