In the photo, the killer brandishes a hammer - the signature weapon of the protagonist in "Oldboy" - in a pose similar to one from the film.Ironically, the film--and the trilogy--is about the ultimate futility of revenge. Of course, with all his references to Christ and crucifixion, it's equally plausible that Hui was "inspired" by The Passion of the Christ. Even more plausible, he saw Taxi Driver, and went the way of Travis Bickle--or some bizarre combination of the three.
The 2003 film, directed by Chan-wook Park, won the Gran Prix prize at the Cannes Film Festival in 2004. The second of Park's "Vengeance Trilogy," the movie is about a man unjustly imprisoned for 15 years. After escaping, he goes on a rampage against his captor. In one scene, he dispatches over a dozen henchmen with the aid of a hammer.
The connection was spotted by Professor Paul Harris of Virginia Tech, who then alerted the authorities, according to London's Evening Standard.
I don't know what this proves about violence in cinema. It's not as if we blame late-night AM UFO talk shows for the babblings of street corner schizophrenics, though the two are sometimes indistinguishable. Cho Seung Hui was clearly mad, and madness is its own way of seeing.
Update: Grady Hendrix makes the connection in just the right way.
The "Vengeance Trilogy" is difficult, painful to watch, and obsessed with depicting revenge as the ultimate act of narcissism—a way to wallow in your problems and proclaim "Oh, poor me" with a hammer.