What killed the child in "The Promise"?

Did I miss someone describing the fatal wound on the little girl's skeleton in "The Promise" on March 30, 2023?

The episode shows that two shots were fired and the killer's first bullet grazed her skull, causing pain and a scar on her skull but not making her unconscious, let alone dead.

The little girl, standing on an outdoor bench, then put out her hand toward the killer. Much like prince Alexei Romanov (1904-1918) is said to have held out his hands while being shot. The next bullet went through her hand and through her body and entered the body of her mother.

So where did the second bullet go through the little girl? I think I remember that there was a bullet hole in her clavicle or collarbone.

As far as I know there are no vital organs behind the clavicle. Of course there are important arteries in many different parts of the body, and if an important artery behind the collarbone was severed by the bullet she could have bled to death rather swiftly.

Someone said the last thing the girl would have seen was the the killer shooting at her. That statement made by a forensic scientist seems to imply the second bullet instantly killed the girl. Thus she wouldn't have seen or felt or known anything after being shot and lying on the ground dying more slowly.

So how could she die instantly?

The human heart is usually a few inches below the clavicle. So a bullet through the clavicle should not hit the heart. Nor would a bullet through the clavicle go through the brain, another way to kill someone instantly.

So the forensic scientists never mentioned what organs or blood vessels the second bullet struck in order to kill her - apparently instantly.

Does anyone remember any statement about the cause of her death which I might have missed?