The video, posted on YouTube by Steven Anderson, shows Anderson arguing with an Arizona Department of Public Safety trooper through his car's closed window. Someone tells Anderson to close his eyes. The DPS officer then breaks the passenger-side window and shoots the Taser at Anderson. The man squeals in pain as the clicking of the Taser sounds in the background.
At first glance, the use of the Taser seems to violate a policy adopted by most Valley police agencies. When Tasers were first introduced, police used them against suspects who simply refused to obey orders or resisted arrest not by force, but by sitting down or pulling away from an officer's grabbing hands. Such use was later prohibited in most agencies when police realized Tasers could potentially be harmful to some suspects.
However, the DPS could probably make the case that Anderson was a threat to officer safety because he had control of his vehicle. Once the agents and officers decided to pull him out of the car (a questionable decision, itself), they must have decided to Tase him right away to prevent the possibility of the vehicle driving off with an officer stuck in the window.
Anderson claims he was repeatedly Tasered even after being dragged from his car, but that's not shown on his video. Anderson does include surveillance footage he obtained from the government, but the camera angle obscures a full view of the take-down.
DPS says the agency is still reviewing the incident.