1. This photo, which shows what appears to be the second of two explosions, was widely shared on Twitter immediately after the event:
  2. This photo shows Boston Police responding immediately after the blasts:
  3. Boston Police confirmed an explosion at 3:39 p.m. ET:
  4. Boston Police later confirmed 22 injuries and two fatalities:
  5. The Boston Marathon said on Facebook "two bombs" had exploded, but it did not give a source for that information:
  6. The AP is reporting two unexploded devices were found at the scene:
  7. Reports of additional devices were being made by 4:30 p.m. ET:
  8. The FAA has blocked the airspace directly over the scene of the blasts:
  9. Local reporters, bystanders and spectators tweeted reports from the scene: