Police probing the deadly shootings at Virginia Tech University have criticised the decision of US network NBC to show footage of the killer.
Cho sent the material to NBC News
Cho Seung-hui sent a package of videos, photographs and writing to NBC on the day of the shootings.
But police said on Thursday that the videos - showing an angry Cho ranting and pointing guns at the camera - added little to their investigation.
A total of 33 people, including Cho, died at two locations on Monday.
Eight students are still being treated at Montgomery Field Hospital, close to the university campus, hospital officials say.
Seventeen were treated for injuries after the shooting, with four undergoing major surgery.
NBC broadcast new footage of 23-year-old killer gunman on Thursday and defended its decision to use Cho's videos.
"I'm not sure we'll ever fully understand why this happened, but I do think this is as close as we'll come to having a glimpse inside the mind of a killer," Steve Capus, head of NBC News, said on the network's Today programme.
Cho's package contained 1,800 words of text and 43 photos, 11 of them showing Cho aiming handguns at the camera. He also sent 28 video clips.
Speaking at Virginia Tech, Steve Flaherty, superintendent of Virginia State Police, said he appreciated NBC's co-operation, but regretted the decision to broadcast the tapes.
"A lot of folks saw images that were very disturbing," he told a news conference.
"This is a kind of image that people in my line of work have to see, and I'm worried that people who are not used to seeing them had to see them," he said.
NBC's Mr Capus said he understood that many people would disagree with the decision to broadcast.
"There is no way to look at without being profoundly upset, and it is incredibly disturbing."
'I will no longer run'
In the first set of videos aired by NBC, on Wednesday evening, Cho was shown ranting at the camera and railing against rich, privileged students.
He blamed others for forcing him to kill.
"You had 100 billion chances and ways to have avoided today.
"But you decided to spill my blood. You forced me into a corner and gave me only one option. The decision was yours. Now you have blood on your hands that will never wash off," Cho said.
"I didn't have to do this. I could have left. I could have fled. But now I will no longer run," the gunman said.
Police have already revealed that Cho, who moved to the US with his family from South Korea in 1992, was admitted to a mental health unit in late 2005.
He was sent for evaluation after two female students made complaints against him, they said.
Police say the same gun was used at both locations, but they have not definitively linked him to any of those killed on campus or proven that he was at West Ambler Johnston at the time of the shootings there.
Two people were killed at the West Ambler Johnston Hall, a university dormitory, at 0715 on Monday.
Two hours later Cho killed 30 others, plus himself, at the Norris Hall complex across campus.
The complaints by students against Cho were made in November and December 2005, around the time Cho's English teachers raised concerns over his writing and general behaviour.
In the aftermath of the shootings, teachers and fellow students have spoken of Cho's extreme moods, violent writings and unpredictable behaviour.
Meanwhile, police locked down schools in California on Thursday after a man threatened a copycat killing spree that he said would make the Virginia Tech massacre "look mild".
More than 12,000 children were locked into schools at Yuba City, north of California's state capital Sacramento, after Jeffery Thomas Carney allegedly made his threat.
Police and Swat teams have launched a manhunt for Mr Carney, a suspected user of methamphetamine, a powerful stimulant.