I am thankful everyone survived this incident. I do believe in karma, and what goes around comes around. I would think if you had the plates, yeah right...you were looking at the plates while the explosion is going on, you'd be able to do something.
Best you can do is file a report. Talking to the police will help you with your options.

Moving forward - is this the first time vehicles have bothered this horse? I would spend lots of time training with vehicles, motorcycles, and bad mufflers, just to avoid this happening again.

Use your talents, that's what they are intended for.....
Gus's Training Log