I don't know anything about aviation..but I did see a show years ago about a new prototype US helicopter...and the first image on Wired, to me, 100% reminded me of it. Googling, I'm sure what I'm talking about is the RAH-66 Comanche.
The angles on the tail roter look similar however according to reports the downed helicopter was carrying half of a 25 man seal team so it had to be something bigger if the government was telling the truth.
I'm not saying it's a Comanche..just saying there are similarities (to me) and it might provide a starting point to see what/where the upgrades modifications came from.
http://en.wikipedia.org/wiki/Boeing/Sikorsky_RAH-66_Comanche
Do a google images search, the thing looks [relatively] identical.