Kansas City resident Mack Nelson said he remembers the days he used to trust police officers. As a kid, he recalls they’d give him high fives, baseball cards and bubble gum. But in a Monday interview with The Star, with his face numb after receiving several stitches from where his head hit the pavement, he said he feels differently now. Nelson doesn’t remember much about the early morning hours of Aug. 8, but a bystander does. The interaction between Nelson and an officer in a gas station parking lot near East 55th Street and Prospect Avenue was caught on tape by Steve Young, who was standing a few yards away. Young, the co-founder of the Kansas City Law Enforcement Accountability Project, arrived at the scene after Zachary Garrard, 31, was shot and killed driving toward officers in an SUV that had been reported stolen. Young’s group, KC LEAP, aims to hold officers accountable in excessive force situations. His phone was out and recording when an officer threw Nelson to the ground....