© @GlobeDavidLRyan/Twitter
Multiple outlets and law enforcement officials are reporting what a horrific looking scene makes clear: The headquarters at the Boston Marathon have been locked down after two explosions were reported near the downtown finish line mid-Monday afternoon, near the Boston Library. Boston police confirmed that there were two explosions - and casualties - but were not saying who or what might be responsible. "There were two booms heard from near the finish line inside the Fairmont Copley Plaza Hotel," reports the AP. Here's one of many images flowing in from social media current scene there:
Just heard that bombs went off at #boston marathon finish line
- Chris Chanyasulkit (@chanyasulkit) April 15, 2013
Video of an explosion near the finish line:

We're going to link to this shot (WARNING: Graphic) since it shows the chaos and some of the injuries, and NECN's Jackie Bruno reports that the injuries there are gruesome:

© @theoriginalhawk/Twitter
I saw people's legs blown off. Horrific. Two explosions. Runners were coming in and saw unspeakable horror.
- Jackie Bruno (@JackieBrunoNECN) April 15, 2013
According The Boston Globe, there are dozens injured though there are varying reports on the number of injuries:
BREAKING NEWS: At least dozens of people have been seriously injured, a Globe staffer on the scene says.
- The Boston Globe (@BostonGlobe) April 15, 2013