The Virginia Tech gunman sent photographs, videos and writings to US broadcaster NBC in New York before he died in the massacre that left 33 people dead, authorities said.
NBC said it turned the package to authorities today.
"This may be a very new, critical component of this investigation. We’re in the process right now of attempting to analyse and evaluate its worth," said Col. Steve Flaherty, superintendent of Virginia State Police.
MSNBC News reported that the materials appeared to have been sent between the first and second shootings at the university. The package, which includes writings, videos and photographs, was received Wednesday.
Cho Seung-Hui shot 32 people to death and committed suicide Monday at Virginia Tech in Blacksburg, Virginia.
Details emerging today, that he was accused of stalking two female students and was taken to a mental health facility because of fears he was suicidal - added to the rapidly growing list of warning signs that appeared well before the 23-year-old went on a rampage.
Among other things, Cho’s twisted, violence-filled writings and sullen, vacant-eyed demeanour had disturbed professors and students so much that he was removed from one English class and was repeatedly urged to get counselling.
In November and December 2005, two women complained to campus police that they had received calls and computer messages from Cho, but they considered the messages 'annoying' not threatening, and neither pressed charges, Virginia Tech Police Chief Wendell Flinchum said.
Neither woman was among the victims in the massacre, police said.