You need to first of all call emergency service (911) to get him an ambulance.
If you want to do something you could apply first aids.
First, check its pulse. With your second and third fingers on the side of the neck or its wrist search for its pulse.
Then, you need to check if he is breathing. Get closer to him and hear.
If he's not breathing, you could straighten its jaw and block his nose to blow on its mouth.
And then you can start CPR to try to get the start to bomb again.