The Virginia Tech gunman sent photographs, videos and writings to 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 on Wednesday.
"This may be a very new, critical component of this investigation. We're in the process right now of attempting to analyze 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.