Oldboy and influence
At Slate, Grady Hendrix does a good job analyzing Oldboy vis-à-vis Cho. Earlier, Stephen Hunter in The Washington Post dismantles the thematic links between the Park Chanwook movie and the VT massacre, though he detects some resonances with John Woo's The Killer. (For The Dizzies original review of Oldboy, go here.)
(Link via the Jdawg.)
UPDATE: A sentence in Wikipedia says that detectives suspect Cho did watch Oldboy repeatedly before the killings; the link is to a Sky News article.
And: Rereading my review (see above), I noticed this quote: “If I knew it was fifteen years, it would have been easier to endure.” Daesu has been imprisoned, for no reason he can imagine, in a hotel room for a decade and a half. Cho came to America in 1992—that is, 15 years ago.
UPDATE (4/23): In the Times, A.O. Scott sticks it to Hunter.