(Adds media group, CNN comments) By Randall Mikkelsen WASHINGTON, April 19 (Reuters) - U.S. television networks limited broadcasts of a video manifesto by the Virginia Tech killer on Thursday after heavy coverage drew criticism from police and victims' families. NBC News, which received the manifesto in the mail on Wednesday, said it had acted responsibly in showing the images and rants of gunman Cho Seung-Hui. But NBC and rival networks said they would use restraint in the future. The images dominated U.S. news coverage on Wednesday evening, two days after Cho killed 32 people then himself in the deadliest shooting rampage in modern U.S. history. "We had planned to speak to some family members of victims this morning but they canceled their appearances because they were very upset with NBC for airing the images," said NBC's "Today" morning program co-host Meredith Vieira. Police investigating the shootings in Blacksburg, Virginia, were also critical. "We're rather disappointed in the editorial decision to broadcast these disturbing images," state police chief Col. Steve Flaherty said. "The world has endured a view of life that few of us would or should ever have to endure," he said. Cho, a 23-year-old student, mailed photographs of himself posing with his guns and video railing against rich kids and debauchery. The package was mailed to NBC after he killed his first two victims on Monday morning but before he cut down 30 more in classrooms. Common Sense Media, which monitors media impact on children, said it had received many calls about the broadcasts from anxious parents. "This is really gruesome and scary stuff," organization head Jim Steyer told Reuters. "People have said could they have used a bit more discretion." Experts also said the images could resonate with potential copycats envisioning a deadly sequel. THE 'MIND OF A KILLER' NBC acknowledged the images were probably devastating to the victims' families. But NBC News President Steve Capus defended the decision to air them. "This is I think as close as we will ever come to being inside of the mind of a killer, and I thought that it needed to be released," Capus said on cable channel MSNBC. NBC said it contacted authorities when it received the material on Wednesday and used it only after "careful consideration." NBC, which let other news outlets use some of the images, said in a statement its news division would limit use of the video to "no more than 10 percent of air time." ABC News cut back to showing still excerpts from the video or muting the audio, but left video images on its Web site. "Once you've seen it, its repetition is little more than pornography once that first news cycle is passed," Jeffrey Schneider, senior vice president of ABC News, said. CBS Corp. <CBS.N> unit CBS News said it would use the images "only when necessary to tell the story." "I would be surprised to see much usage of it," spokeswoman Sandy Genelius said Fox News said "we see no reason to continue assaulting the public with these disturbing and demented images," but it would reserve the right to use them again as needed. Fox is a News Corp <NWSa.N> unit. Images from the manifesto were also scarce on Time Warner Inc's <TWX.N> CNN on Thursday and a network spokeswoman said it would use the material "very judiciously." Flaherty said the material turned out to be of little value to investigators. NBC is owned by General Electric Co <GE.N>. ABC is owned by Walt Disney Co. <DIS.N>. (Additional reporting by Michele Gershberg and Jeremy Pelofsky)
