On Tuesday, the Associated Press reported that a “senior U.S. intelligence official says Russian missiles crossed into NATO member Poland, killing two people.”

This story ripped through big media outlets which blared “BREAKING NEWS” — see from CBS.

It tore through Twitter.

There would be a series of followups, see how the story morphed on archive.today. The story featured a host of bylines including John Leicester, James LaPorta, Vanessa Gera, Zeke Miller (White House correspondent) and Michael Balsamo.

One version featured the headline: “AP Source: Russian missiles cross into Poland during strike.”

One story AP ran was not bylined and just one sentence: “A senior U.S. intelligence official says Russian missiles crossed into NATO member Poland, killing two people.” This violated AP’s already minimal rules: “Stories that use anonymous sources must carry a reporter’s byline.”