Marathon Bombing: U.S. Heightens Security In the Wake Of Boston Explosions

Earlier today in Boston, Massachusetts, two explosions, one following the other by about 15 seconds, went off at the finish line of the Boston Marathon at Boylston Street. Kylie Atwood of CBS reports there appears to have been a third explosion set of by police.  Authorities are still scrambling for answers; whether or not this was a deliberate act or an accident remains to be seen. At 4:05 p.m. (EDT) Boston PD confirmed two people dead and twenty-three wounded. Boston Marathon officials are describing the explosions as having been caused by bombs. Cities are locking down; as a precautionary measure. In Washington DC, Pennsylvania Avenue is a swarm with secret service police, and New York City is vamping up security detail.