New York Times public editor Margaret Sullivan called for “systemic change” after the newspaper wrongly reported that accused San Bernardino shooter Tashfeen Malik posted publicly on social media about jihad.

As iMediaEthics wrote, on Thursday, the Times added an editor’s note to its story correcting its claim about Malik posting her jihadist views publicly. In fact, her comments about jihad were posted privately in messages.

On Friday, Sullivan weighed in with a blogpost calling the error “a bad” mistake that also involved anonymous sourcing.

“It involved a failure of sufficient skepticism at every level of the reporting and editing process – especially since the story in question relied on anonymous government sources, as too many Times articles do,” Sullivan wrote. Sullivan has criticized the Times several times previously for its over-use of anonymous sources.

“I have two major and rather simple questions: How did this happen? And how can The Times guard against its happening again?”

New York Times executive editor Dean Baquet admitted to Sullivan “this was a really big mistake” and that the newspaper needs to “do something about how we handle anonymous sources.” According to Baquet, “our sources misunderstood how social media works and we didn’t push hard enough.” That the Times‘ anonymous sources for a story on a mass shooter’s social media habits wouldn’t know “how social media works” is shocking, iMediaEthics notes.

Sullivan repeated her recommendation that the New York Times cut back on anonymous sourcing and called for the newspaper to “slow down the reporting and editing process” and “show far more skepticism – a kind of prosecutorial scrutiny – at every level of the process.”

Sullivan reminded that the Tashfeen Malik social media story is the second time recently that the New York Times had to amend an important story for errors — previously, the newspaper had to correct its reporting on Hillary Clinton’s e-mails. Two New York Times reporters, Matt Apuzzo and Michael S. Schmidt, worked on both of those stories, but Baquet noted to Sullivan that they cover “two of the most sensitive beats in Washington – national security and law enforcement.”

Sullivan pointed to the Washington Post‘s Erik Wemple’s reporting on the error and its significance. Wemple noted that the claims that Malik posted publicly about jihad and was still allowed in the U.S. became a topic at the recent GOP debate.