[durt]

Give me a hammer, I'll fix that

[Ferocity]

THAT is a "winged scapula."
Notice where the butt stock of the gun is at... Cuddled right next to his ribs. The force of the kickback+the location of the gun must have damaged his "long thoracic nerve."
He didn't dislocate his shoulder at all... as far as I can tell, he practically severed his long thoracic nerve.
Who knows
I'm not a doctor
Seriously though
That happens when your serratus anterior muscle is not opposing any of the other muscles attached to the bone named, "the scapula."
Not a laughing matter = )