Do you think the driver knew he was under arrest when he was tasered? I don't. The officer never told him he was under arrest. How was he to know?
“Turn around and put your hands behind your back NOW,” repeated twice by a police officer holding a Taser shouldn’t be met with “What the heck is your problem?” and walking away, in my opinion.
When an officer has you in his custody and control you are under arrest. The officer does not have to tell you that you are under arrest.