Isn't there usually a launch alarm sounded before firing?
Or maybe the general quarters order didn't apply to him? 
I've seen almost the exact same view as that guy did. Whenever we did a live fire, the whole ship knew about it, and everyone who wasn't actually at their position was on deck to watch the big flashbang go off. My buddies and I were crowded in the Helo Hanger jockeying for position. I'd forgotten my mickey mouse ears. Holy crap that was THE loudest thing I've ever heard. I'm surprised I don't have tinnitus from that day lol.
Anyhow, yeah, that guy knew exactly what he was doing if you ask me. I bet he made some money off of it too.
-Sik