These were created by NYC Light Brigade and The Illuminator ("a political art project that emerged out of Occupy Wall Street") who use light projections to display their messages. As of last night at 12:10am, they were airing the stream from outside of BAM on Lafayette.
Yesterday afternoon's explosions at the Boston Marathon killed 3 people, and injured over 100 (with dozens still in critical and serious condition). The FBI has taken the lead on the investigation, which is ongoing. [via NYC Light Brigade]