Flash Mob Sings ‘Amazing Grace’ at RiverTown Crossings Mall in Grandville [Video]Flash Mob Sings ‘Amazing Grace’ at RiverTown Crossings Mall in Grandville [Video]Holiday shoppers at RiverTown Crossings mall in Grandville received a big surprise when a flash mob sang "Amazing Grace" on Saturday.Matt MilhouseMatt Milhouse