Kids causing trouble at the track

As me and my training partner were doing a few intervals together we came around turn 3 at the Asheville Mellowdrome. Something was apparently flung from the other side of the wall and landed right in front of my tire and hit my partner in the face. She said it felt like sand. What I saw hit the track in front of me resembled an orange bungee cord. The second time around I notice that some "children" were on the other side of the wall. I've seen these kids there in the past taunting the riders while they do their group workouts, even as much as standing in the track in front of us. We are on fixed gear bikes with no breaks so we cannot stop fast.

On the 3rd time around I slowly rode up to the wall and whipped out my cell phone and took a picture of them. Once they realized what I had in my hand they pulled their shirts up over their heads and ran fast!