Considering how thin most interior doors are, a 40 grain LRN or even a 36 gr. HP should be able to punch through with no trouble.
A "neck" is unprotected flesh with major blood vessels having no bony protection. At the distance the perp was from this young man, either bullet would still be moving fast enough to do some serious damage.
Granted, shooting through the door doesn't allow placement of the shots, but he could have also shot the guy in the eye, causing incredible pain and panic.
The fact that he was able to do as much as he did even after being wounded himself says a lot about this young man's character and his parent's training.