Olly spotted the firstie from before standing at the Slytherin platform. "Hey!" He called, hoping the boy would look his way and see what he intended to do. He didn't know his name so that was the most warning he could give under the circumstances. Without waiting another second, he threw the ball as hard as he could toward the young Slytherin. With the state of the gravity in the room, it should have no problem reaching its target.