Hassan, a biology major who wants to be a pediatrician, said Friday he did as he was instructed to do, fearful of police with rifles pointed at him. He dropped his keys out the window, got out of the car with his hands raised, walked backward as instructed, and then fell to his knees so officers could cuff him. He asked repeatedly why he was pulled over, but police would not acknowledge his questions as they searched his car, he said. They did not find a gun.