The boy had a fake gun, and he was looting from somebody while caught, the rangers then caught him, and as shown clearly , the boy tried to get hold of the gun from the ranger, anybody in the armed forces will tell you, if somebody tries to get hold of your gun, you need to decapitate them, the boy was also at fault, instead of going for the gun, he should have staright away layed on the ground, and the fault on the rangers part is that get the boy on the ground instead of pointing a gun at him. The US police and other law enforcement agencies do this, straight away get the subject to get on the ground, the boy did not, the rangers did not force it, and even after the shooting , the rangers should have got the boy to hospital, they got him to hospital after he got dead. And why did the cameraman stood there, he could have got the boy to hospital?
So alot of people at fault, and also the training methodology.