回複：請老貓看看：孩子騎自行車被汽車撞了，汽車走掉了

I think you have the case because of :
1) Your son is only 14, what he said does not mean he could have the ability to make a right judgement, especially after a car accident;

2) Obviously, your son had witness, and that driver did not treat your son properly, that was why the police got called by someone.

3) Your son had the body injury and property damage.

You should check with local attorneys who like the car injury case, they might do something in favor of you. The problem, if you like to spend the time, maybe very time comsuming.