Today in History - April 16 | Gunman shot two, mailed a package, then shot 47 more
Seung-Hui Cho killed two dormmates and then mailed a package to NBC News.
He then walked into a classroom building and shot dozens of people in the space of nine minutes.
A student who witnessed the massacre said Cho carried out the shooting "without even the slightest emotion on (his) face".
By the time police arrived, Cho had taken his own life.
Two days later, the package arrived at NBC, full of photos and a video manifesto.
In his rant, Cho railed against wealthy students.
He also included many photos of him posing with guns and knives.
Much of the scrutiny after the massacre came from a failure to act on Cho's behaviour at the university.
Professors and classmates recalled Cho as being disturbed, mean and threatening.
Cho had been ordered to receive treatment as an outpatient at a psychiatric hospital, but did not receive it.
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