An Iowa trooper pointed his gun at a motorcyclist and knocked him down for no apparent reason during a traffic stop, then falsely charged the man with eluding law enforcement, according to video and documents reviewed by The Associated Press.The sheriff in eastern Iowa's Cedar County said the officer's behavior amounted to excessive force and misconduct, and it's among the reasons he recently announced he would no longer book any suspects the officer arrests.Dashboard camera video shows then-Iowa State Patrol officer Robert Smith pulling over motorcyclist Bryce Yakish for speeding on Sept. 25, 2017. What appears to be a routine stop escalates immediately when Smith runs from his car with his gun drawn and strikes Yakish in his helmet's face shield. The force knocks the 150-pound Yakish backward and onto his bike, and both he and the vehicle fall to the ground. Yakish is then repeatedly heard complaining of neck pain."Something is wrong with my neck," says the Davenport man, who was 20 at the time.The Cedar County attorney's office released the video in response to records requests, after initially claiming that it was confidential and could be withheld. The office has issued a disclosure known as a Giglio notice to suspects indicating that Smith, now an officer in the small town of Durant, may not be a credible witness due to prior inaccurate testimony.The release came after pressure from media outlets and Sheriff Warren Wethington, who argued that the video's disclosure was legally required and in the public's interest."It's pretty damning," the sheriff said of the video.Wethington noted that Smith didn't activate his emergency lights and siren while speeding on Interstate 80 to catch up to Yakish, who had sped past Smith's squad car.Smith pursued Yakish to an off-ramp near West Liberty and then turned on his lights and siren. Yakish pulled over in a gas station parking lot promptly, got off his bike and put his hands up.Smith ran at Yakish with his handgun in his right hand and pointed at the man. He used his left hand to strike Yakish in the helmet, knocking him down.