Boston Marathon explosions
"We will find out who did this. We'll find out why they did this," President Barack Obama said.
Reports are streaming out of Boston after two bombs exploded near the finish line of the Boston Marathon. We've aggregated a list of sources for live coverage of the explosions.
All the Boston Marathon runners who listed themselves as being from Columbia have been accounted for and appear to be OK.
Agencies were also stepping up their social media response, telling the public via Twitter and Facebook to report suspicious activity to the police.
Obama also told Mayor Tom Menino and Gov. Deval Patrick that his administration would provide whatever support was needed in responding to the incident, the White House said.