In one sad sense there was nothing new, or even very unusual, about the televised killing of two journalists in Virginia on Wednesday morning.

Death on TV has occurred with frightening regularity ever since the advent of the medium: Jack Ruby’s shooting of Lee Harvey Oswald, the assassination of President John F. Kennedy, in 1963; and the Sept. 11, 2001, fall of the World Trade Center. The prospect of death appearing suddenly on our screens is as common as it is ghoulish.

Yet in another way, the video of the Virginia shootings posted by Bryce Williams, whose real name is Vester Lee Flanagan and who is thought to be the gunman who killed two of his former co-workers at the television station WDBJ, is a frightful twist in an age of online sharing and ubiquitous video documentation.

The killings appear to have been skillfully engineered for maximum distribution, and to sow maximum dread, over Twitter, Facebook and mobile phones. The video Mr. Flanagan shows is an up-close, first-person execution. It was posted only after his social media accounts had become widely known, while the police were in pursuit of the killer. And unlike previous televised deaths, these were not merely broadcast, but widely and virally distributed, playing out with the complicity of thousands, perhaps millions, of social networking users who could not help watching and sharing.