Story of the day: The AP twitter feed was hacked, and "reported" that there was an explosion at The White House, injuring Barack Obama.

The tweet looked like this. It came just after 1 PM ET.

Of course the story was false, though it remained uncorrected for several minutes. Eventually an AP employee tweeted that the company's account had been compromised.

But in that time, the stock market briefly tanked.

The Dow had been up over 100, but it then lost 150 points.

The market did recover.

So how did that happen that a tweet caused the market to dive?

It's not that everyone on Wall Street is watching AP's Twitter.

But here was our inbox from when it happened. Brokers instantly started emailing everyone with the headline, before walking it back.

We've blacked out the names of the folks passing on the tweet.

Bottom line. Stuff moves really fast from Twitter to trader inboxes and then to the market itself.