Here we go ...

WASHINGTON, July 7 (Reuters) - The United States is raising the terrorist threat level for rail and mass transit systems, but not for airlines, after the bomb blasts that rocked London, a U.S. government official said on Thursday. The official said the alert level for trains and subways would be raised to orange, which signifies a high risk of terrorist attack, from yellow, the mid-point on the five-point color-coded system.

The DHS website is here, if you want to keep track of the (inevitable) changes.

You can also read the text of the statement from the group claiming responsibility for the attacks.

And here's the UK Muslim leadership's response, condemning (of course) the attacks.

Let's hope we don't see a surge of retaliatory violence. That is the last thing anyone needs right now.