He’s just stupid and immature is all. The kind of thing a 13 year old boy might do and get punished for.
But he’s 20 years old. He has a screw loose. Or drugs.
In any case, while I see why she was bugged out by it, I don’t think it is the end of the world here.
So if a stranger sneaks up and grabs your shoulders, will you just shrug and say it’s not the end of the world?