"My grief is unbearable. Is this real? Am I going to wake up?"

Andy Parker, whose daughter Alison was shot dead live on US TV, says he has not watched the shocking footage and will not watch it, the Washington Post reported.

"It's like showing those beheadings," he said. "I am not going to watch it. I can't watch it. I can't watch any news. All it would do is rip out my heart further than it already is."

But the shootings of Alison and cameraman Adam Ward, who also died at the scene, along with their interview subject Vicki Gardner, who survived, were all too real, as are the images. They have prompted renewed debate about the ethical media use of graphic imagery as well as warnings about the risk of psychological harm from viewing it.

The New York Daily News received a furious response on Twitter when it posted its proposed front page with disturbing images of the shooting splashed across it. CNN was showing the station's version of the video on the hour. In Britain several newspapers including The Daily Mail, The Daily Telegraph and The Sun ran front-page images of Alison Parker at the moment she was shot.

Two video versions exist, one broadcast live and filmed by the cameraman Ward for his employer and the other filmed by the murderer, disgruntled former co-worker Vester Lee Flanagan II. The gunman reportedly shot himself during a later highway chase, but not before he uploaded the shootings to his Facebook and Twitter accounts. They were widely circulated for 10 to 15 minutes before the social media companies suspended his accounts and removed the video.

Not much more than a year ago, after MH17 was shot down in Ukraine, it seemed a new frontier in media when pictures of bodies were circulated on social media and published in traditional media, overturning a convention of traditional publishing to keep bodies out of the picture.

Now, with the killing of Ward and Parker, we are dealing with actual footage of the moment of death. Many people watched the footage inadvertently due to the autoplay feature introduced by Facebook and Twitter a year ago which means videos pop up and play in users' newsfeeds whether or not they have chosen to watch them.

"Social media is the Wild West of news publishing", where content is unfiltered by editors and reproduced often without consideration of impact, said journalism academic and social media specialist Julie Posetti.

While the risks of inadvertent broadcast of graphic material are as old as live TV, the Virginia shootings demonstrate how "the perpetrators of acts, and witnesses to them, can self-publish videos and images which are then propelled into our newsfeeds across multiple platforms", Ms Posetti of the University of Wollongong said.

"Journalists and citizens alike are increasingly exposed to content that they can't 'unsee'," she said. But the imperative to compete or keep up with "citizen journalism" was resulting in "declining standards within traditional Western media with regards to publishing graphic imagery" and concern about desensitisation, she said.

Clinical psychologist Rob Gordon, a leader in the treatment of adults and children surviving trauma, said it was "very important that people do not underestimate the disturbing effect of material such as this".

He said seeing images of the incident actually happening was potentially far more harmful than hearing or reading about it, especially to people who have themselves experienced violence or trauma. Those people are "very likely to have some reactivation". The "direct sensory quality" of the footage triggered much deeper, more intense emotions.

"People who are struggling with or carrying tragedy really need to keep away from that stuff, just like a person with a compromised immune system needs to keep away from someone with a bad cold," Dr Gordon said.

He urged parents to protect their young children from seeing the videos and to be aware that they may be talking with their friends or classmates about the incident. Parents need to help their children put the incident in a context which is far removed from their everyday lives - "that allows the children to say 'I don't need to worry about it' ".

The best remedy for any trauma from seeing the footage is to talk with someone about it, Dr Gordon said, because that "changes it from input to output in the brain" and "disrupts that loop with the emotion and images going around and around".

He said people should consider turning off the autoplay function in their social media feeds, because it was important to have control over the images they see. "The spontaneous 'Oh my God, what is this', that is going to go in much deeper."

Exceptionally violent videos are not new to Twitter. One Twitter user pointed to a seeming double standard in the response to the video of the Virginia shootings compared with footage of violence against black people in the US.  Ms Posetti said it was "perhaps because the victims in this case were traditional information gatekeepers, as was the alleged perpetrator".