I can tell instantly that it's an Unreal2004 mod. I worked in that piece of junk engine for so long in college. Ugh. It's a shame that it's the easiest 3d engine to get a license for, since it's so completely ass backwards as far as building levels and shit goes. Unreal3 engine was a huge upgrade. Valve's engine (I'm blanking on the name for whatever reason) is awesome too, though going from Unreal2004 to that is difficult, since they work kind of backwards from each other.
Not a bad Sion model though. All they need to do now is mod the lightning gun or something into a black barrel replica and they're golden.