In an effort to make this original post less chaotic, I'm rewriting the post with the details as known at this point. This rewrite occurs at 01:00 Eastern US time.
The Event:
Video of Explosions. Viewer Discretion Advised.
At 14:50 local time, two hours after the first runner crossed the finish line of the Boston Marathon, an explosion occurred near the finish line behind a barricade where spectators were gathered to watch friends, family, and strangers finish the run. 16 seconds later, a second explosion occurred approximately 100 yards away on the runner approach.
Boston Police responded immediately, having been on scene with the national guard for event security. The local area was placed on lockdown, with nearby mass transit and local bridges closed. Motorists were advised to evacuate the city. The bomb squad was called in in order to dispose and/or disarm any other explosive devices found. There was a controlled detonation of at least one suspicious object. Five other objects were identified as potential explosive devices throughout the city, however, it does not appear all of them were explosives.
Cities around the world increased their security presence. US government buildings were placed on high alert.
It is unclear as to the nature of the explosives. There have been rumors that trauma doctors have been removing BB-sized ball barings from wounds, which suggests a handmade shrapnel explosive.
Casualties
As of this writing, there have been three confirmed deaths and 144 injuries. At least one death is rumored to be a 9-year-old boy.
Motives
As of this writing, no individual or group has been has been declared a suspect. There was no specific warning of an attack, although police are searching a suburban apartment in connection with the case.
The FBI will lead the joint investigation. A 20 year old Saudi exchange student injured in the bombing was a person of interest and was guarded at a local hospital while questioned.
JFK Library
There was also a fire at the JFK Library 5 miles away, which resulted in no injuries but some damage. The BPD commissioner originally stated there was an explosion at the library and that they may be connected, but have since stated that the incident appears to be fire related and does not appear to have any connection to the Boston Marathon event and was instead a fire in a mechanical room.
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Original 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
This post will be updated as more information becomes available or confirmed.