The S.S. agent doesn't moved - the view switches briefly from a different camera angle, whence you can see WJC on the other side of HRC, switches back to first camera, where you again see S.S. guy.
Supposedly professional actor stumbles and and trips on (his own?) words.
Didn't have enough time to rehearse the script? Nervous some, no?
POTUS totally puts him to shame - delivers off-the-cuff - all the while
incorporating coded messages. Kek!