Lighting effects in compositing

I was watching the preview video for the real-time compositing feature and one moment really grabbed my attention. As you can see in this video 1:25 the lightning strikes the post and destroys it. The interesting thing is how the actor also is affected by the lightning strike: blue glow + shadow. Can someone explain how this is done? I reckon it’s just an additional (physical) light inside the studio where this is shot that is switched on at that exact moment.
However I’m wondering if it’s possible to have in-engine light sources somehow affect the actor?