The ghastly video of a killing that police say was uploaded to Facebook Sunday by the suspect himself is a natural extension of several dark trends of the social media era, psychologists and other experts said today.

“What we have found in our work is that certain individuals full of rage seeking global attention do one of two things: They maximize casualty rate, as you see in the spree killings; or they do something cruel and innovative,” like in this video, said J. Reid Meloy, a forensic psychologist and clinical professor of psychiatry at the University of California, San Diego.

No one but Steve Stephens, the 37-year-old Cleveland man who police believe filmed a fatal shooting as he committed it, knows exactly what his motives were for posting the video. In it, a driver strikes up a brief conversation with a stranger on the street, then shoots him dead, zooming in on the victim’s bloody face with his camera. Stephens is still at large, and no notes or internet posts have surfaced giving an explanation for the killing.

But he would not have had to look far for precedents: In August 2015, a gunman in Roanoke, Virginia, filmed himself shooting to death two former colleagues, a cameraman and a reporter, and posted the video to Facebook. In June 2016, a Frenchman who sympathized with the Islamic State shot to death a policeman and his partner, then posted a live video boasting about the killing just afterward. One act was personal and the other political, but the convenience of streaming with a phone amplified the act, and the horror, globally.

Movies and TV shows have been dramatizing the effects of posting videos of such cruel, random killings for at least two decades, when an episode of the police series “Homicide: Life on the Street” featured two young men filming themselves shooting an older person to death.

In the video posted to Facebook, the driver asks Robert Godwin Sr., 74, a retired foundry worker, to say a name, Joy Lane, whom some reports identify as Stephens’ former girlfriend. Then, just before the shooting, the driver says to the camera: “Yeah, she’s the reason this is about to happen to you.”

If a breakup was behind the gunman’s devastation, the killing is one type of crime of passion, forensics experts say. That is what some psychiatrists call a “righteous slaughter,” a murder committed with complete indifference to legal consequences and understood, on some level, as “a last stand in defense of one’s basic worth,” as described by Jack Katz in his book “Seductions of Crime.”

Now, the technology to amplify such grievances, and reach a vastly wider audience, is readily at hand.

The ability of emotional videos and other material on social media to become “contagious” and prompt reactions through a community or audience depends on the content, studies suggest. But few psychiatrists doubt that, for a great number of viewers, a graphically violent video of such blatant cruelty can itself be a traumatic experience: The pain, the rage and the message are, indeed, amplified.

Meloy said that killings in public settings had increased during the past decade, despite decreases in violent crime overall.

“One consensus factor among researchers is the presence of social media, which guarantees saturation news coverage, which in all cases magnifies attention to both the act and the actor,” Meloy said. “Such perpetrators can hunger for both a target and an audience.”