That was effing great.
That kind of effect, sound, and so on made our familiar happy little "lol lets go play" garden was made genuinely scary.
I actually think that that's something that could do with being incorporated into KF, like a mod or something. A change in lighting, sound, and other things. In fact, it'd be really cool if Tripwire advertised their game in such a style, and it would make the gameplay of KF even more hilarious - it's always had some comedy to it.
As for the video itself, as I said, I reeaaally like the effects, but I think putting in FPS action gameplay kinda took away from that. Mostly because there was no shooting noises (echoy blasts ringing out would work here) and their length just kinda made them... not scary. While very pretty, they weren't entertaining either. If I were you, I would have made those action sequences really short, in-your-face, noisy, and genuinely scary sounding, rather than actiony.
But all in all, great stuff, and I hope to see more! :>