I watched it again. I don't think he threw that as a punch. Looking at his hand, that looks like an intended nerve strike to the BP. He's not even making a fist - he is hitting with the tip of his thumb.

I'd bet this guy has been through a PPCT course or two.

Don't know what causes it but some folks can't reason how to act before things even get to that point. Worked with a client, a true monster, in state hospital that almost killed (brutally beat) a police officer while he was handcuffed. Will probably never get out no matter how he behaves from now on. Had everyone on edge when he walked past you. I could write a book on the things he did. Got special treatment from staff because he was so intimidating.