In the first few seconds in the video, you can see Ted Cruz (R-Texas) start to ask his question to Rand Paul (R-Ky.) and then someone walk past him and give Cruz a fist bump on his shoulder before exiting the chamber. That was Paul leaving for a few moments just as Cruz was beginning to ask his question. Paul wasn't being rude by leaving, but he was acknowledging Cruz's help in giving him a break. Paul can hold the floor even while he's not the in the chamber. Paul has been assisted by several senators today, who have asked him questions in order to allow Paul breaks. Cruz, and other senators such as Mike Lee, John Barrasso, Ron Wyden, Marco Rubio, and Jerry Moran have been providing Paul with some key assists in this filibuster.