Take photos of the scene from various angles.
If you whacked his windscreen then the judge will probably "do you" for this. You could claim mitigating circumstances I suppose. Ask the witness to come to court.
^
At least you are not injured. So you have a sore fist after breaking the windscreen. It seems a flimsy one if you can smash it with your fist.
Anyway best of luck for June 8