Fox News reported that an “ISIS-linked” Twitter account warned of today's shooting in Tennessee before it happened, but the tweet in question was sent after the attack had ended. The falsehood was propagated by anti-Islam blogger Pamela Geller before spreading through conservative media

Four Marines were killed when a shooter fired on two military sites in Chattanooga, Tennessee. Fox News reported that the attacks may be connected to ISIS because an ISIS supporter purportedly discussed the shooting on Twitter before it happened. Fox host Sean Hannity repeated the false claim on his radio show.

In fact, the tweet Fox News referenced was posted well after the shooting had already occurred. Mashable editor Brian Ries first pointed out the discrepancy.

On Your World, Fox's chief intelligence correspondent Catherine Herridge reported, “the last investigative thread I would mention at this point is that we're taking a hard look at a Twitter account -- an ISIS-linked Twitter account -- that seemed to have foreknowledge of the shooting in Chattanooga. The tweet went out at 10:34 with the hashtag Chattanooga referring to American dogs and a likely shooting. This of course was about 15 minutes before the shooting took place.”

On his radio show, Fox News host Sean Hannity also referenced the inaccurate information.

HANNITY: We have a report from Robert Spencer's Jihad Watch, that he's put together -- a timeline regarding today's, what they are now calling a domestic terrorist act in Chattanooga. We have four Marines that have been killed. By the way, our thoughts, our prayers are with the families and the entire military community there. According to the AP, the shooting started around 10:30, 10:45. The Islamic State tweeted a warning about the attack, posted at 10:34 a.m. The ISIS tweet specifically mentioned Chattanooga, which is an obvious reference to the attack. If it's true that ISIS was taking credit for the shooting at the exact same time, or maybe slightly before the shooting commenced, that would be pretty strong evidence of a connection. And Spencer reminds us the Islamic State has called on Muslims to murder American military personnel here in the U.S.

Fox repeated the claim in further segments on Your World, The Five, and later on Special Report.

The source of the claim is conservative blogger Pamela Geller, who has a long history of anti-Muslim activism.

Geller made the claim on Twitter and on her blog, writing, “This morning an ISIS supporter tweeted this at 10:34 am -- the shooting started at 10:45.” The report cited by Hannity from Jihad Watch cites Geller as the source. Spencer has often worked with Geller on anti-Muslim projects.

But the tweet was posted at 1:34 p.m. Eastern time, not 10:34 a.m., as Geller asserted. According to news reports, the shooting “unfolded at two sites over 30 minutes” and started “around 10:45 a.m. ET.”

The image of the tweet she references on her blog appears to be stamped with the Western time zone -- Twitter time stamps are based on the user's time zone, not the time zone of the person who made the tweet.

Media Matters took this screenshot of the ISIS supporter's Twitter account at 5:13 p.m. ET, and it shows that the post was made 4 hours previously (near the 1 o'clock hour Eastern time).

Conservative blog Weasel Zippers also made the erroneous conclusion about the tweet in a post headlined, “Islamic State Account Tweets Warnings About Chattanooga Moments Before Shooting Began.”

UPDATE: After this story was published, Fox News began to pull back on their allegation. From Special Report with Bret Baier:

BRET BAIER: Let me be careful about the tweet to the ISIS-related account. In Garland, Texas we know that it came out before the shooting, before that happened. In this case, the time stamp does say 10:34, but we don't know if that's Pacific time, Mountain time, Eastern time, so we have to be careful about it coming out before the shooting. Point is there are ISIS accounts that are pointing directly to this incident and touting it as one of own.

UPDATE #2: On The O'Reilly Factor, this story was addressed at least three more times.

At the top of the Factor, O'Reilly reported the “sensational” ISIS tweet story, even after admitting it wasn't “exactly clear whether it's accurate.”

Midway through the show, Catherine Herridge reappeared and admitted that “there are now some questions about the time stamp on one of the ISIS tweets earlier today.” When O'Reilly pressed her on how she learned about the tweet, she said, “I first saw it this afternoon, it was part of the social media that was circulating.”

At the end of the Factor, Special Report anchor Bret Baier clarified the timing of the tweet, saying that “all indications now are that it came out after the attack.” When O'Reilly asked if that meant the ISIS tweet story was “a bogus situation,” Baier replied, “yeah.”