SAN FRANCISCO • It looked almost like a first-person shooter video game: A handgun in a man's grasp comes into view. A woman appears in the man's sights. Shots are fired.
But this was no game. It was the chilling video taken by a killer of him stalking his prey - two television journalists broadcasting live for a station in Virginia that fired him for erratic behaviour in 2013.
A small audience witnessed the attack live on television. But Twitter and Facebook became the unwitting conduits of the video, inflaming debate on when it is okay to show violence on social media.
Two videos showing the shooter's perspective of the incident were uploaded on Facebook and Twitter, where they started to go viral. The footage was quickly removed from both sites.
"This seems like we're turning a new page in the Internet era," said Endpoint Technologies Associates analyst Roger Kay. "It's definitely a new frontier. Except for ISIS (Islamic State in Iraq and Syria), really nobody has done this."
ISIS extremists have used social media to share videos of beheadings to advance the group's cause through terror, but the shooter's video marked the first time "a freelancer" operating for personal reasons used the shocking sharing tactic, according to Mr Kay.
Twitter users, including a number of journalists, had urged others not to retweet the account that posted the clips.
"Our #WDBJ crew was literally ambushed this morning," Mr Brent Watts, chief meteorologist at the station, wrote in a tweet. "Please DO NOT share, or post the video."
Reporter Alison Parker of WDBJ- TV in Roanoke, Virginia, was conducting an interview at Smith Mountain Lake during a live broadcast on Wednesday morning when she and cameraman Adam Ward were shot and killed.
The man identified as the shooter, Vester Flanagan, later shot himself on a nearby interstate highway and died at an area hospital, said the authorities.
Both Twitter and Facebook have removed the accounts that posted the videos.
Twitter spokesman Jim Prosser pointed to the firm's media policy, which says it can delete tweets and suspend accounts in violation of its rules. Users cannot post threats of violence, promote violence or use excessively violent media in profile, header or background images.
Facebook's community standards prohibit using the platform for criminal activity as well as to celebrate crimes committed. Copies of the first-person shooting video posted on YouTube were similarly quickly taken down, but at least one copy was still visible late on Wednesday with a search as simple as "Virginia".
"I know it's a sad occurrence, but leave a Like so this can spread faster," a YouTube user who uploaded a copy of the shooter's video said in a chat forum beneath the post before it was removed. "It's not something you 'Like' to see but this is the only way it will be seen by others."
Adding the television broadcast view of the shooting to the online video sharing mix also raised questions on whether it should be considered acceptable to display graphic news footage on websites - but not the view taken by the shooter.
"What's the difference between this guy posting his stuff on Twitter and Facebook, and Yahoo taking the TV footage and putting it on its front page?" Mr Kay asked rhetorically. "The same sensationalism is operating in both cases. It's sort of a spectacular video."
AGENCE FRANCE-PRESSE, BLOOMBERG