Two images of a game called Agent appear in his portfolio, each with four screenshots. Rockstar is mentioned in the file name of the images; he’s also done work for Grand Theft Auto IV. The images claim the visualization was done in 2009, meaning the game’s probably progressed much further — if the images are legit, that is.
See the pair below. In the meantime, we’ll mail Rockstar.
Also of note, he’s listed himself as a Senior Environments Artist on Grand Theft Auto V, which he dates for release in 2011.
Thanks, Gamer’s Mint.