Obama: Bombers Will 'Feel Full Weight of Justice'

President Obama says the United States does not know "who did this or why" but vowed that whoever is responsible for the explosions at the Boston Marathon "will feel the full weight of justice." Obama made his remarks this evening from the White House about three hours after two explosions detonated near the finish line. "We will find out who did this and we will hold them accountable." The president said the government would increase security around the United States "as necessary" but did not say whether his administration thought the incident was part of a larger plot.

Obama has been in touch with federal law enforcement and Massachusetts officials in the aftermath of the explosions, and he promised that any federal resources they need will be provided. "The American people will say a prayer for Boston tonight," he said. Additionally, the president spoke with Republican and Democratic leaders on Capitol Hill, saying that "on days like this, there are no Republicans or Democrats, we are Americans united in our concern for our fellow citizens." (More Boston Marathon bombing stories.)