AP reporter via Think Progress.
They were in the VIP seats and were not injured.
As always, the Boston Marathon was held on Patriot's Day in Massachusetts. Per Charles Pierce, Patriot's Day was important to Timothy McVeigh, and possibly still is to others of that ilk.
Pennsylvania Avenue in front of the White House being closed off for security.
Boston NBC affiliate has an updated story. There was a memorial to the 26 victims of Newtown at the 26 mile point.
Confirmed that it was an intentional bombing. Three undetonated bombs found, one rendered "safe".
Good news: Per ABC, noradiological material was included in the bombs.