The president and first lady traveled to the Cathedral of the Holy Cross in Boston Thursday, a show of support for a city that lost three people Monday and saw scores more battered and maimed when bombs exploded near the Boston Marathon finish line.
The Obamas attended a prayer service hosted by the city's spiritual leaders, a chance to pray for the victims and for a quick arrest in the case.
"We will all be with you and you learn to stand, walk and run again. And you will run again," Mr. Obama said.
He also vowed to bring the perpetrators to justice.
NBC News has learned investigators are focusing on two men they've spotted on surveillance video shot near the bomb sites.
The pair are seen talking on cellphones, while dropping bags or backpacks in the spots where the devices exploded.
The race is on to figure out who they are, where they are, and why they did it.
At a house hearing Thursday morning Homeland Security Secretary Janet Napolitano deflected criticism that the investigation is moving too slowly.
"This is not an NCIS episode," Napolitano said. "Sometimes you have to take time to properly put the chain together to identify the perpetrators."
In addition to first responders and local officials, the president set aside some time to meet with victims recovering from their wounds.
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