I would also like to know!! Maybe his new Survivalist skin for the Sturmgewehr? I have it as well, looks dope!
I actually know the answer now as they posted it again in another thread and someone spotted what they were trying to highlight. When they bring out the syringe their shadow stands up for a second.
Still nothing to do with the Boys though 
This is the bush wookie starter pack. Dice sucks major donkey you know what.