Is This A Quality Bluff Or A Stab In The Dark?

Summary: It's the final table of a $500 tourney with $270k up top, and one player makes a bold move with 9 remaining. Is it a good move or just blind aggression? FLOP: 8d 9c 2d TURN: 2s River: 4d Vuong: 10s 10d Alex: As 8c For access to exclusive Poker Guys freerolls and other tournaments on Nitrogen Sports Poker Room, use this link to sign up: www.nitrogensports.eu/r/632610 ***Our Book is NOW AVAILABLE! Get "How Can He Fold???" here: www.thepokerguys.net