One person was killed and multiple children were among 21 injured after a mass shooting at the Kansas City Chiefs' Super Bowl victory rally on Wednesday triggered panic among huge crowds of fans. Children's Mercy Hospital in Kansas City, which takes patients up to the age of 17, said it was treating 12 people -- 11 of them children, nine for gunshot wounds -- after the shooting, which unfolded just moments after Chiefs players had addressed a vast crowd of cheering supporters gathered nearby.