Poor thing. How many times did he have to do that run?

Yes, that was what I was thinking of, but on that scale you would need to remove the reflective objects and perhaps put a snoot on the flash (rolled up piece of black card would do it) to narrow down the flash area. It would also help to have infinity space behind him so the flash had no effect behind him. A beach at night would be good - do you have a beach nearby?
What flash were you using?
If anyone else wants to try this and post results here, please do.