In the saturation coverage that followed the Connecticut school massacre, some in the media made an awful mistake.

While fragmentary reports after a mass shooting are often marked by errors, it is difficult to imagine a worse blunder than identifying the wrong man as the killer.

It began on social media, which reported that Ryan Lanza, the 24-year-old son of a teacher, was the shooter. Images of Lanza’s Facebook profile spread across the web. (The media wrongly reported that Lanza's mother taught at the Newtown elementary school, a mistake that was initially repeated here.)

CNN, MSNBC, Fox News and CBS reported that Lanza was the shooting suspect. So did Slate and the Huffington Post. “Ryan Lanza Facebook Page Shows Suggestive Details of Apparent Newtown, Connecticut Shooting Suspect,” said the HuffPost headline. Some reports attributed the information to investigators.

But Lanza, whose profile picture was shared thousands of times online, posted vehement denials on his Facebook page, such as: “Everyone shut the fuck up, it wasn’t me.”

And it wasn’t. The news outlets later corrected their stories, saying police had identified the shooter as Adam Lanza, 20, who is Ryan Lanza’s brother.

This was an egregious error, a product of a fast-moving media culture in which getting it first often supersedes getting it right. Accusing the wrong man of perpetrating a massacre in which 27 people, including 20 children, were killed is about as bad as it gets. And in the Twitter age, that misinformation spread around the globe as ordinary folks amplified the mistaken media accounts.

Blogger Jeff Jarvis, who teaches journalism at the City University of New York, followed the trail on Twitter and did not name Ryan Lanza in his post. But Jarvis wrote later that he “foolishly did not include a conditional statement in my tweet: I did not say ‘if this is the account of the killer, then…’ Or I did not say this was the ‘alleged’ or ‘reputed’ account of the person named as the killer. These are basic, basic journalistic skills drilled until they are reflexes and I would use them in any story for print. I didn’t use them online.”

When Gabby Giffords was shot in the Tucson massacre last year, some media outlets erroneously reported that she had died. Fortunately, that turned out to be as false as the initial reports from Connecticut.