Dear Joseph,
Once the person is safely off the road, (i. e. he was not pulled over) the Police can let him go. Happens all the time. In this case, they do not even know if he drove impaired. Besides for the cop telling him to move the car.
The Officers chose to arrest him, and they have to live with their choice. He chose to resist and he died for it.
A taser is not a deadly weapon. You wrote that above. When Police hold it, it is non-lethal. When used against Police, it is deadly. Well, I could sort of agree considering these two cops bumbled for the greater part of an hour over how to get a drunk out of the way. I wouldn’t let them touch my water gun.