Vandalism on Children's Playground

I have just returned from the playing field where I have been on my hands and knees sweeping up small, sharp edged stones. These had been deliberately spread all around and under the toddler climbing frame. The black surface is rubberised to reduce injury. These stones on top however, would badly cut any little one falling on them.
There is no area on the playing field where these stones exist so the act is deliberate. I need to go back with a bigger broom to finish the job. Please take care with little ones.