I think the child was running, then turned around, with the replica gun in hand...and that when he was shot. The bullet went into his temple and just above the ear. So he could not have had his back turned at the time.
Besides, if a dangerous armed robber is running towards other people, with the gun in their hand, it is legal to shoot a fleeing felon to protect others. They had no idea he was 13 with a fake gun.
So it is not just about being a that to the officer but it is about allowing a dangerous person to flee into the public and harm others in an effort to get away. He could have taken a hostage or carjacked someone.
ETA:Tyre suffered a gunshot wound of entrance on the left temple that passed left to right and slightly downward and exited through the right temple. The entrance wound was above the left ear and the exit wound was in front of the right ear. Tyre also suffered a gunshot wound to the left collarbone area. Lastly, he suffered a gunshot wound to the left flank. There is an exit wound on the right flank.
He could easily have been shot in the temple while looking back over his shoulder. He was also shot in the side toward the back.
The was 13.